Perhaps they are mandated when they apply for a gambling license that they should ask KYC for a certain threshold. But the thing is that some casinos, not all of them are using this to somewhat used as a excuse to not give the winnings of some gamblers.
They they to hide from it to that point that even if you presented them with your legitimate personal info like passport, they are not going to accept it.
As far as hacking though, not sure what casinos are you referring, but it seems by today's standard, casinos are hard to break unlike before. They could be one of those that really secured their websites and their wallets to prevent such breach.