Parents will get their kids phones worrying that they're missing out. The more parents do that the more the kids without phones are actually being left out. If the government puts restriction on these things than parents are much less likely to worry.

I've heard of parents of children for a certain grade getting together and all signing a pact that the kids won't have phones until a certain point, say 16. It only goes into effect if something like 75% of the parents for that grade sign on. I like that idea.