Monero is actively used in the casino to ensure the anonymity of transfers, so that it is impossible to track payments and calculate the winner.
And you're forgetting licensed casinos are combating against money laundering, they wouldn't give easy for any gamblers that using Monero to gamble on their casino. I think any gamblers that using Monero will be asked to submit KYC regardless how much the amount. This will help them to track about the account activity and which address the gamblers will send their coins to.