Somewhere I read : Younglings these days use twitter and snapchat for daily life events and reserve Facebook for bigger in-frequent events (birthday, get-together, trip etc)
Personally I get on Facebook twice per year, once on my birthday and once before summer to tell the world where I'm working.
That's about how it goes, then every once in awhile a new app will come up like house party recently, and everyone will jump on for a month or so then go back.