For a child who is young enough for their parents to choose a system for them, I know far more parents who would get the 3DS because it doesn't have a phone in it ...
It might be different in different countries/regions, but around here it seems like most parents don't want their children to have phones until they're in their teens. Certainly, you see the occassional 11 or 12 year old with their own cell phone, but it doesn't seem to be a common thing for kids to have until they're 16 or 17. On top of this you wouldn't (typically) substitute an item your teenager wanted with one they didn't want if they were similar in price; because if you ever did this and happened to get them something that wasn't cool, odds are good that it would never be used (or might get destroyed).
