And if they do it with their own money, it's their phone.

Children prior to 18 are not subhuman. If you're old enough to buy your own phone, you're old enough to decide whether and how to use it.

The idea of treating under 18s like they are human is extremely undesirable in the USA because it among other things opens up a lot of doctors to be held accountable for their participation in the mass mutilation of baby boys. It also holds a whole lot of physically abusive parents to a standard where their children could call CPS and get their parents in legal trouble for corporal punishment.

Of course, these are indeed good things in worlds that don't endorse physical violence as the primary method to enforce control. This is why Finland his tail docking, ear cropping, animal crating, corporal punishment, circumcision, etc bans and why the US South is so ruthless.

This is unhinged.

Are you a parent?