I'm nowhere near off my rocker. I don't know what country you're from but every casino I have ever went in here in USA makes you give your I'd to be scanned and checked. Hence performing kyc basically up front.
I assume you are talking about in store casinos. In UK if you win big then they ask for KYC or you are allowed to go and through away your money.
I dont think it's too much to ask for a casino to perform their check before allowing someone to gamble vs allowing someone to sign up, play, win huge, and get told fuck you we aren't paying you until after you pass kyc. It just looks shady as hell to do it that way.
Even say all clients are checked KYC upfront, in a popular online casino there are thousands of registrations. Not all of them are real. Now, send request to KYC all of the accounts to KYC providers. You are literally asking to waste money. It's not really logical at all. Casinos are business not charity.