Note: personal opinion bellow It seems to me that the overall interest in Facebook is decreasing. The social network hasn't had any interesting feature added to it in the last couple of years. It's becoming boring and boring, so that's why I believe people are leaving. Still, Instagram and WhatsApp are running strong with barely no competition. We don't see any news about their user base decreasing and news channels…
Note:- I have been off FB for the past 5 years or so. As much as I hate FB and its abhorrent privacy policies, there are a very large population who do not care about privacy. I have some in my household who don't and FB's latest financial results prove it.
I think John Oliver did a pretty good job of framing the Snowden revelations in terms of "the NSA can see your penis". That's a good angle to make people care.