I mean KYC is pretty basic thing. They need to know who you are legally by gambling and casino regulations based on the geographical laws in which it resides. I guess for a casino they see that you can't pass the KYC requirement to claim the winnings therefore the transaction is void and the house wins. IF someone was to argue that in a court of law and they can't even answer some simple KYC questions I think they have some other problems that they make for them selves there. The casino knows this and thats why they get away with it.
Casino can asked KYC anytime to their members and members must do if they wants to withdraw their money or don't wants to have a problem while they playing gambling on that casino. Doing KYC can avoids them to waits for some time, especially if they wants to withdraw their wins. Many gamblers doesn't like KYC because they thinks that they don't have to do that, especially if they playing gambling at the crypto casino. But with the regulations from the government makes them to obey the rules and if gamblers really doesn't wants to do KYC, they can search for the other casinos. But today, with the interfere from the governments, many casinos asked KYC to their members so gamblers will not gets casino that allows them to avoids KYC. But gamblers should search for the trust and reputable casino to avoids the problems after they doing KYC.