Phone calls are for emergencies at this point. If it's not it's spam. Then Apple ruined SMS ( except for the US apparently?), nobody wants to gamble whether a message will reach a phone or the iPad sitting in a drawer still associated with the phone number.

So social things, like communicating with people, happens on social apps.

Kids also would be better with map apps, GPS, electronic payments and auto-charging bus/train pass if you expect them to have any independence.

All in all, kids should be the last ones IMHO to get real dumb phones. We might as well give them pagers if that's what we're going for.