I mentioned at the beginning of my post that many online gambling websites do this kind of thing. I did not mention all the websites through this post.
Gambling websites can, of course, investigate every account, after big wins. But when it goes to the extra stage, it feels bad to everyone. Only because that player wins a large amount does he suddenly become a bot account, suddenly asking for different documents! All of these things are frustrating for a gambler. So finding the best gambling website and play on that platform is the most important thing for gamblers.
Because their aim isn't to stop money laundering. In reality, they use money laundering to benefit themselves (this doesn't apply to all casino). Have you seen any casino that asks for KYC when you deposit money or when you lose money? Do they ask you to KYC in order to admit your lose or otherwise they'll refund the funds?
No, they ask KYC because they know that many people aren't willing to submit their KYC documents and sometimes they prefer to leave funds instead of sending these documents. Casinos know that very well and they are becoming "anti-money launderings" once you try to withdraw. Again, it doesn't apply to every casino.
When you win, they suddenly care on money laundering, otherwise who cares if you lose (lost funds are always clean funds for them from their logic and don't require further investigation).
This is beyond the imagination of most gamblers. They want more deposits on their website so they do not block any user while making a deposit. But that shows the real look when that user goes to withdraw. However, some casinos are involved in this type of work, not all casinos do this type of work.