A Wired article from earlier this year describes how a regulatory change in Russia (suddenly prohibiting most gambling) flooded the market there with old slot machines. Some technically skilled people bought those machines and figured out the rules by which they operate in great detail. They then used that knowledge to classify the operation of similar machines in the US, making predictions about what button-press timing would lead to improved payouts, and use those predictions to guide their gameplay and win money.
This seems very similar to a common purpose for entering casinos: people go in, at least thinking they know the rules of a game and intending to use that knowledge to win money. Most of them do win money. Only some walk away with a net gain, but those folks are then touted as example customers so that more people will be convinced to come in and place bets.
However, the folks who learned how the slot machines worked and use this to win by playing well were then prosecuted and jailed for years as perpetrators of fraud. What is the particular law that they violated? What is the threshold where it's considered fraud if you know too well how the game works? Why does the casino get the option of prosecuting players as criminals instead of making the tradeoff between accepting losses vs. using better pseudorandom number generators?