The temptation of youth to try illegal substances is not just a problem in sports. In all environments you will have age restrictions.  To say that we should uphold the ban for the sake of children is as if we would advocate a ban of alcohol for everyone, because some teenagers like to socialize with adults who are legally able to drink alcohol. There is always going to be an age restriction and it is the duty of institutions, trainers and athletes to uphold it, so that later in life as adults, athletes can make an informed decision.