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Crypto casinos can afford that luxury because they are in total control of the coins on their platform and you are just gambling with digits on a screen. Some casinos accept 0-confirmation transactions. You can play as soon as their system recognized the receiving transaction. It doesn't need to be confirmed. But if you get lucky and win, your deposit transaction has to confirm before you can withdraw your winnings. They can't lose their own money by accepting unconfirmed transactions. Only the players can lose.
Honestly - I've heard of casinos that operate their service like that, but forget what the name of the casino is. Of course - when a casino or certain service has allowed its customers to see the balance in the wallet before the transaction is confirmed, then they have prepared terms and conditions before the customer withdraw their money. Casinos don't want to lose - every feature should benefit them from a business perspective.