Which casino are you talking about precisely MonsterV? Because most of crypto casinos I know don't require KYC (including the one you're promoting) unless you're not a rather big winner. Bitcoins and other cryptos allow players to gamble quietly without being bored by issues with their bank or their state authorities prohibiting gambling at offshore casinos and all nice games.
With bitcoin gambling there is no need for kyc for online casino's. Its advantage is that countries where gambling is not allowed can can take part in gambling while the down side is teens under 18 can also take part in such online gambling platforms. It's just a double edge sword IMO.
I don't understand why it's a matter if they are under 18. This is not porn websites or dark marketplaces. It's up to their parents to monitor them. Moreover when you are under 18 you usually have not much money to spend, and rarely a rent to pay then risks of losing big amount is pretty low.