Yeah, but that assumes, that there are people out there, selling smartphones to children at scale. First the price for one is way to large for the financial budget of a child, and second that gets even more price-intensive, after the first one got confiscated by the parent.
There are literally people out there selling smartphones to children at scale. A smartphone these days can be bought for as cheap as a burger because 2nd hand market exist and its not limited to iPhones.