This can be done even by people who have no intention of doing so. But that's the nature of cryptocurrencies, so like it or not, it's difficult for authorities to track the funds (even if the person isn't doing anything outside of their country's tax laws).
This is the reason why you’d see some casino operators making it mandatory that all deposits are to be wagered for a specific number of time. - so that users won’t just make deposits and instantly withdraw it to a different address without having to play or risk it but if there are requirements that would make them risk the money they are to launder they would have to reconsider and use a different method.
I don’t know much about this but casinos have been actively trying to battle this type of money movement - they have been trying to restrict withdrawal in accounts that look suspicious or have activity that resembles money laundering.
Does such rule and wish to mix funds with casino funds via deposit/withdrawal really work? User deposit to a specific address all the time, he get withdrawal from a bunch of accounts only. Casinos account address are only one more address in chain. All the addresses are transparent anyway. And it is not hard to generate one address for every user, and bind it on him only. I doubt that anything is mixing properly with deposit/withdrawal through casinos.