The age limit placed on people below 18 year to keep them away frim gambling have not been most effective as we have hard records of under age gambling in many place and this is a pointer that casino has indeed misolaced their primary responsibility which is to prevent that from happening and that is why there is need for KYC.
Casinos have provided regulations by not allowing underage children to gamble. And even though casinos have implemented KYC for their members, that can't stop minors from registering and gambling. They can do KYC using the identity of adults around them, which helps them gamble. Perhaps, this can be reduced if each parent pays more attention to supervising their children using devices connected to the internet so that their children do not visit casinos.
This is really a matter of discipline and communication inside the household.
If the parents are hands on on their child and provides all the basic necessities, educates their child about the consequences of doing impulsive, illegal, and risky decisions in life, then there's a small chance that these kids will be inside a casino establishment or website given that the values, principles, and the upbringing they were exposed into has a positive and strong foundation about doing good things, obedience, and not being involved in things that will not be beneficial and is prohibited to them.
It all really boils down the measures the parents do for their child not to be lost and to the child himself, the willingness of following his parents as his role model, not giving into the curiosity and peer pressure, if there is any.