I would like to know how many gamblers in the crypto operate with amounts of millions of dollars. In my opinion, there are very few of them and they are unlikely to be anonymous, since if the casino makes transactions of several million dollars without knowing the information about the client, it can be accused of money laundering.
There are fully decentralized casinos already, aren't there? Not with a lot of games though, but I think there are. Most casino are compliant and have no issues with clients betting in the 100k to a million range. It's just that the casino must be able to handle these clients.
Can you provide links to such casinos? I doubt. First, most likely they do not have the liquidity to ensure the game at such high bets. Secondly, even if it is possible to make a decentralized blockchain for a casino, how do you make a decentralized site for a casino? I have not heard anything about such solutions.