The problem is peer pressure and the fact that most parents want to have a way to be in contact with their children at all times. You could get your kid a flip phone, but your kid is going to be an outcast if anybody finds out.

Then you're in the wrong school district. This is certainly true in some parts of the US. We went to a lot of trouble to make sure we lived somewhere (a fairly safe and affordable part of a very walkable, diverse large east coast US city) where this would not be a problem, and it has paid off. Having a flip phone is not an issue here (in middle school).

Some random suburb, especially where the parents aren't super educated, is usually going to be hell for this though. A lot of parents who don't know/care/are too impoverished in terms of time or knowhow, end up just using the smartphone as an all purpose babysitter (much as TV in the 80s and 90s) from toddler or even baby age on.

It's always been the case that when you choose where you live you choose what kind of peers your kid will have, and therefore, to a degree, what kind of person they'll become, but smartphones have dialed this effect up.