Well, some gamblers prefer to stay anonymous when they gamble. Its one of the reason why they dont want to comply to kyc specially they're just an average gamblers. It would be better if this is optional on a casino. If you want to raise your limits then you need to comply on their kyc requirement otherwise you can play without worrying about it.
It bloody has no purpose if it was "optional". I mean, users would just simply avoid using it anymore, and besides, KYC isn't something that is supposed to be optional, it's supposed to be something pretty much guaranteed by the casino to be done to users once a certain criterion has been met. Even then honestly, they still hold the right to do KYC even if you didn't meet the criteria, all because they're pretty much the owner of the casino, nothing we can do about that.