Thats fair enough.
The casinos which accept zero confirmation deposits have no risk of capital loss, and can only at most lose the deposit the customer placed. If the customer wins, they will not be allowed to withdraw until the deposit confirms. If the customer loses and double spends their deposit, then at most the casino will lose their deposit, and will then ban their account and IP address.
I think you know it is trivial to change your IP address. Unless the casino is requiring KYC prior to playing, it is also trivial to create a new account. You can use a mixer to hide blockchain evidence you have played at the casino previously.
If a gambler is allowed to gamble their deposit, and their deposit never confirms, if the gambler had a net losing bet, the house edge will effectively have been lowered, possibly to something below zero. A negative house edge is going to result in the casino losing money over the long run.
A deposit not confirming that was allowed to be gambled, will pretty much always mean the customer took some action to intentionally prevent the deposit from confirming. This will pretty much always be because the customer's balance is less than the deposit amount (they lost money gambling). A customer will generally have no reason to prevent a deposit from confirming if he is a net winner in his wagers.