On any forms of business, there will always be abusers like that but business owners can do something to stop them. If it's an online casino then they can increase their website's security and they can also enforce a KYC to intimidate those who will try to abuse their sites but if ever the abusers insist to and they are caught out, it will be easier for the casino to trace them.

Some criminals will just hack someone's account that are verified already by a KYC and they will use it for their exploits. Problems like this will be solved out easily if a user who got hacked will cooperate on the casinos immediately and then the casino will freeze their accounts.