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.
By the need for kyc you said, do you mean the normal kyc process that is available in most online gambling casinos right now, or is there any other special kind kyc you are referring to?
Asking because, passing kyc verification is currently available on most Casinos, but that still have not stopped underaged gambling, as I've read in several stories, under aged gamblers still have a way of passing kyc verification easily, and one of those ways to by verifying their account with the documents of an up to required age uncle, brother, sister, parents, or any other family member.
So for me, I think that if the battle against underaged gambling must be won, then online gambling casino must introduce a much more stricter process of kyc verification, and parents too have an important role to play in making sure that their children does not go into gambling underaged.