For what it is worth, service by publication is not allowed in a lawsuit to collect a credit card debt, although certain kinds of substituted service reasonably calculated to give you notice (e.g. via text message or a facebook direct message) can be authorized by a court in a suitable case. But, skip trace firms and private investigators are very good at finding people, especially with this kind of debt at issue. Unless you go completely off the grid and grow your own food, somebody can usually find you.
Also even if you can't be served, the credit card company could, if it could locate assets belonging to you, bring a lawsuit and attach the assets, tying them up until you could be served with process, possibly by substituted means.
Now, if you simply don't have any assets or income, the credit card company knows that it can't get blood out of a turnip and may not bother. But, usually, people with no assets or income aren't permitted to run up $100,000 of credit card debt in the first place.
In addition, it wouldn't be uncommon for a credit card company to sue to get a judgment on a large debt even if you don't have a current ability to pay because who knows when your circumstances might change in the future for the better, for example, if you win the lottery, or receive in inheritance, or get a better job. A money judgment often lasts twenty years and sometimes can be renewed if it is not collected by then.
Your estimate of the cost of a credit card debt collection lawsuit is wildly exaggerated. A lot of the work is done by paralegals and the total litigation cost would exceed $5,000 only in rare cases. Also, the credit card agreement almost certainly provides that any attorneys' fees and litigation costs incurred are added to the principal balance of the credit card debt, so it is always cost effective to sue.