Comment by ars

In places where WhatsApp is highly used you basically can't function without it, school events are posted there, friends organize activities on it, teachers communicate to both parents and kids on it.

Giving a highschool kid a phone is basically mandatory or they will be cut off from activities, and/or rely on a friend to relay messages. In some places even middleschoolers need it.

There are definitely downsides (not to mention WhatsApp is a really badly engineering program), but the network effect is too strong to fight.