Yes, usage by kids is a real problem. My child is one of only two in the class that doesn't use WhatsApp. All the others do. They have what they call a "class group", even though not everyone is there.

When I try to tell parents how much Facebook learns about their kids (their friends, networks, and by merging data from different sources: habits, school, frequented locations, etc), they just roll their eyes. The response is "well everybody is tracking us, who cares".

All this even though there is Signal, which works JUST FINE.