No benefits at all for the user to submit his kyc. You dont know what will happen once you submitted it.
In crypto gambling, things should be anonymous as most of the casinos are not regulated, only those who are regulated should require KYC but if we have other option we would prefer a no KYC unless we are betting big money in gambling.
what if the casino operator gos rogue and sell all the information or get hacked. That is besides the why question.
If they'll do that, it's already out of our control, but with legal consequences, I doubt they will do that.