Most online casinos are not operating legally so they would rather prefer to deal with "unknown" entities, because they can even allow children to gamble and nobody can point a finger at them for knowing that in advance.

The KYC requirements are more a government requirement within a legal "Brick n mortar" establishment and not really something that can be enforced with online casinos that are operating from some "island" location.

Gambling sites needs money and they dont really care about the identity of the gamer. It means nothing to them if a player less than 18 years plays on the site as long as the player has money to spend. But there are some casino sites that request for KYC and I am wondering what exactly they need it for or reasons why they need it knowing completely well that no player would never agree to submit their private details.
I dont gamble in any site that request for KYC. I cant remember the name of a site a visited some time last year, with varieties of games and I would have really loved to play but as soon as I realized that KYC Is a prerequisite for withdrawal, I just backed out of the site and that was the end.