It's not like talking about using weeds that you tell your friends about but you don't go in public shouting about it. Instead people go to online forums sometimes posting with their real names- bragging about using pirated software.
What is exactly stopping the police from having them arrested?
Not all things that we commonly refer to as "illegal" are actually crimes - many of them refer to violations of contracts or other obligations where the harmed party may (or may not) use the civil system to obtain some satisfaction, but the government and prosecutors will not do it for them.
In general (with some exceptions, depends on jurisdiction and circumstances), most low scale copyright violations are treated as a civil matter - it allows the harmed party (i.e. the copyright owner) to sue you for damages in a civil court, if they wish and are able to do so. However, it generally is not a crime (again, with some exceptions - e.g. large scale distribution often is) so the government and police on their own cannot, should not and does not investigate and prosecute violations of software licence terms.
Mostly, it's because it would be prohibitively expensive to do so. The police can, and probably do, run operations designed to stop piracy, but these usually target the source, because it's usually easier to shut down a network of servers than the millions of people using them.
Even if a user posts something on a forum with something that looks like their real name, it's very rarely verified, and could therefore be anyone that's chosen a name that seems "real enough".
While it may be illegal for people to pirate copyrighted illegally, statutes almost always require the rightsholders to bring a claim - in order to do that, they need to identify the real identity of the person making the claim; in order to do that, they may need a court order requiring the website operator to produce the relevant information.
Even if one assumes that this didn't require a court order for production, this all takes time. Time that you need to pay someone to spend on it.
Of course, this is part of the reason why, in the US, speculative invoicing is prolific when it comes to those few cases where people are pursued for torrenting, even to the point where in the Dallas Buyers CLub case, the Australian Federal Court has specifically required that the court reviews communications to be sent, to prevent this.
From a law enforcement perspective, let's pretend that the various police agencies would work for free to identify, locate and apprehend these people. Then more money would need to be spent actually prosecuting them.
So basically? Enforcement comes down to the financial capacity to pay people to uphold your rights, and the effectiveness of the actions. Why try to prosecute a million people, when you can take out that handful that runs the sites that facilitate infringement?
In part because police has limited resources, as so far other three answers quite clearly and correctly pointed out.
There's also another reason:
Currently, millions of people download movies and feel it is absolutely ok to do that (regardless of what the law might say). Think about the reaction from the general public if suddenly a movie company decided to sue everyone who did that. The backlash would be stellar. Both towards them and towards the government. Neither wants that, of course.
If a law isn't taken seriously by almost anyone, you'd better not enforce it (and repel it as soon as you manage to).
The main reasons are: it takes a significant amount of resources to arrest and prosecute someone, and society views these crimes as less serious than drugs or violence.
In the United States, the police need probable cause to search or arrest you. Since anyone can go online and pretend to be someone else, it is difficult to obtain a warrant for that specific person. In addition the police would have to investigate where this specific person is. Then they would have to establish probable cause to search this persons computer. After all this work it is possible they will find evidence of violation of the law. Afterwards, you have the right to a day in court. What that means: the prosecutor has to establish beyond a reasonable doubt that you violated the law in downloading these files. As a defendant you don't have to prove anything! So if you can make an argument casting reasonable doubt in the mind of the jury, that you acquired these files legally or that your actions did not contribute to violating you will go free.
Another point to keep in mind: the government needs to train police to investigate these crimes. Being a policemen does not pay as much as being a programmer or an IT specialist. Thus it may be difficult to find someone to investigate these crimes.
The police doesn't have infinite time. So they should prioritize their efforts based on the amount of damage that a crime does, the amount of effort it takes to handle the crime, and the likelihood to get a conviction. I suspect that based on this, people using pirated software are low priority.
But more important is that using pirated software is very likely not a crime, but a civil offense. The copyright holder can take you to court and sue you for damages and certainly can make you regret having pirated that software, but they won't get help from the police. So even if you are convicted in court and pay out a lot of money, it is a civil matter, so you will not be arrested by the police.
A very interesting and controversial topic. I see other had already told this is a matter of civil law in most countries, so I would like to leave a quote of Aaron Swartz, an Internet activist.
"The law about what is stealing is very clear. Stealing is taking something away from someone so they cannot use it. There’s no way that making a copy of something is stealing under that definition. If you make a copy of something, you’ll be prosecuted for copyright infringement or something similar — not larceny (the legal term for stealing). Stealing, like piracy and intellectual property, is another one of those terms cooked up to make us think of intellectual works the same way we think of physical items. But the two are very different. You can’t just punish people because they took away a “potential sale”. Earthquakes take away potential sales, as do libraries and rental stores and negative reviews. Competitors also take away potential sales." - Aaron Swartz (UTI interview, 23 January 2004)
Full interview - Aaron Swartz Interview from January 23rd, 2004.
As others pointed out, in most jurisdictions police can't simply go after pirates on their own. The software maker won't do it in civil case, because tracking down and prosecuting a single pirated copy is usually more expensive than the income lost from one copy. But there is also another profit involved:
Pirates learn the software and thus create a market for it.
Let's put an example of Microsoft's Windows and Autodesk's 3DS MAX. Those companies are known for actively hunting and punishing institutional pirates (companies), but don't launch same scale offensives against home pirates. Microsoft is now upgrading all pirated Win7s and 8s into (equally illegal) Win10s while Autodesk runs many contests where works done in 3DS MAX can win the author ... a legit copy of 3DS MAX. Those activities directly benefit home pirates, but they benefit software makers even more. Those people running pirated software will get used to it, learn it and they will become good at using it. When they get a job, they will demand workstations running 3DS MAX on Windows. It will be cheaper for their employers to buy a copy of Windows than to have them re-skilled into Linux. And this is where the profit is made: those companies are much easier (read: cheaper to identify and prosecute) targets, and it's those companies who will pay Microsoft and Autodesk.
Piracy carries huge advertising value. With careful assessment, software maker can extract bigger profits from prosecuting pirates selectively than from trying to make everyone pay. Even in jurisdictions where piracy is a criminal offense, copyright holders would more likely cooperate with police on large scale infractions rather than on single users, so even there the police is given incentive to leave home pirates alone.
We are talking stealing "intellectual property" here and that doesn't involve depriving a person of a physical possession, but the money he or she would be entitled to from sale of the copyrighted property. However, the MPAA and RIAA are far more piratical than the kids who download torrent-based p2p files.
Unless you are a world-class musical act who can write your own ticket, here's the way it worked in the US for my 5-person band when I was a musician decades ago. The production company would sell the CD to a brick-and-mortar store for $10.95. The store would typically sell it for $16.95 and return 25% ($1.50) to the producer. From this $12.45 per CD, the producer pays for the creation of the CDs, cases, labels, warehousing, transport, advertising, lawyers, agents, its own employees, shareholders, and all of the studio people. By the time the money got down to the band it was typically about 35 cents per CD, or 7 cents per musician. Most bands like mine made the bulk of their money touring. Ironically, if a kid pirates a song or album he or she would not have bought, likes the music, and comes to a concert, the band makes more money from the young pirate than they do from a CD sale. Today, with downloadable music, the manufacturing, storage, and transportation costs have disappeared - but the bands' profits have not reflected it. Who's the real pirate?
A note: Carole King and her late husband Gerry Goffen were paid $3,000 their first year of songwriting for AlJohn Music in NYC's legendary Brill Building, $2,000 their second year, and $1,000 their third for all of their copyrights in perpetuity - a mere $6,000 in total. They made money on writers' royalties when their songs were covered many times and from Carole's performing, of course, but they were grotesquely ripped off by the music company for their copyrights until King became famous enough to fight them and renegotiate. This is a matter of record and anybody can look it up.
The irony is that pirating music probably leads to larger audiences at live concerts and, therefore, more money for us struggling musicians without top-tier reputations.
