It's called parenting.
I teach in a secondary school and lots of parents can't be bothered with the arguments of saying NO to a child, so let them do as they please.
I have no issue with my teenager having a smart phone, BUT I get to choose which apps he can and can't have, and I use family link to make sure I can monitor his phone usage, and limit how much time he can spend on certain apps. I have very clear rules/boundaries and he knows the consequence if he breaks them. (e.g. no phone at all).
Absolutely no phone in his room at night. I am so bored of teenagers that are not getting enough sleep due to being on their phones at night!
At my school phones are banned. Any phone spotted is confiscated and the parent collects it. This is to limit bullying during school hours.
The messages I've seen (Snapchat etc...) and screenshots that my tutor group have shown me are often quite vile and it's no wonder some kids feel like shit when they receive messages like that from cowards who hide behind an app.