If you teach someone how to gamble and other gambling activities then it wouldn't be in your control whether he would be addicted or not. It depends on that particular persons characteristics and behaviour. Suppose, someone started gambling as a fun, as the time passes he can get addicted. It is not anybody's control.
True, when a person start to gamble, they need to understand the risk and in order for them to easily understand they need to be matured enough.
There are minors that are gambling now and they can do it since no kYC in most gambling sites, they are at a high risk.