That's true but almost every player out there wants to play on a KYC-free casino. These KYC-free casino would become a target for them money launderers.
If a person comes to " KYC-free casino x" with 100 btc, what should the owner of that casino do? Seize the money? Report the guy to the FBI? Deny service? Or just ignore him?
This is a pretty delicate matter. A person with 100btc very well may be a clean dude.
If that's happen, most of KYC free casino will terminated his account since there's no rules to ask his KYC to get his personal information. They don't have a rules about multi accounts, they don't have a rules about VPN, so they're really free to accept any gambler who want to play on their casino. If the representative ask the gamblers of his 100 BTC, it would be stupid for them since there's no fraudster who admit if he's a fraudster.
But of course there's will be a suspicious activity that can distinguish between an innocent gambler and a fraudster.