Kids aren’t leaving social networks. They’re redefining the word “social.” Rather, they’re actually using the word with the intent of its original meaning: making contact with other human beings. Communicating. Back-and-forth, fairly immediate dialogue. Most of it digitally. But most of it with the intent of a conversation where two (or more) people are exchanging information and emotion. Not posting it. Exchanging it.
Social, as in conversation, where every post gets a guaranteed response and relationships are built to last; not “social” as in mass distribution (Twitter/Facebook) where most posts go unheard because no one is paying attention.