There have certainly been cases where people have used casinos (and even exchanges) to hide/shuffle the origin of funds, 'cause when you deposit crypto on a platform, your link to the platform's address ends and when you go to withdraw, you withdraw funds from different origin (from other customers). Unless the platform keeps deposit/withdrawal logs of all user operations and provides them to authorities when requested.
This can be done even by people who have no intention of doing so. But that's the nature of cryptocurrencies, so like it or not, it's difficult for authorities to track the funds (even if the person isn't doing anything outside of their country's tax laws).
This is of course still possible on casinos that do not ask for your KYC, but if the money comes from an illegal source they are aware, they will notify the authorities and freeze your account and give your money to the law enforcement instead, so whoever does it still takes a risk. So answer is, yes some people have used it to hide the origin of their funds.