One thing you should understand is that making all people pay for the ill intentions and actions of few is usually a bad system design
there are several articles and research online stating how KYC, besides being useless, is costly and adds a lot of friction to businesses
Sites aren't really given a choice in this matter sadly thanks to trash government systems and their excessive regulatory policies which is why they end up enforcing KYC in some form or another to survive basically.
BTC's popularity surge over the years left to world governments trying to take back control in this manner.
Though I was not a gambler before but I know things that happened in gambling halls because I have seen friends, relations playing gamble and mostly in sportsbetting and in those those days the request of KYC was minimal unlike this days. And since I fully and actively from forum last year, I have been seen that the request of KYC is at the peak. And I am suspecting that it because of bitcoin which the government and it authorities can not control so they want to control the users from various organizations and firms. And because KYC was not rampant in those days and when it was introduced in the gambling system many people fall into victim. And many casinos did not ask KYC at the registration time but at the withdrawal time to do and undo customers. But in the other hand, every genuine gambler should provide KYC for smoothly of using the site.