Comment by TonyStr

Following this logic in context of GP's hypothetical, your son would end up taking heroin with his classmates covertly because he knows his father doesn't approve of it...

The point that (I think) GP was making is that it's impossible to raise kids in a different world than their peers. If their peers all have phones, your kid gets left out if he doesn't have a phone. If society bans smart-phones for kids under 15, there's nothing to be left out of since none of them have it.