And yet enough people do that it's a real and recognized problem to the point that HN discusses it every couple of weeks. HN in itself being a similar echo chamber.
People get news from what they look at. There's no such thing as "news". It's all eyeball based. The source with the most eyeballs is considered The News.
Actually, nearly 50% of American adults use facebook as a news source [0]. Not that this means they don't have other sources, but it seems very likely that increased consumption of news via facebook is cutting into consumption from other sources. Anecdotally I've noticed that trend in my own news consumption, to my chagrin.
[0] http://www.niemanlab.org/2016/05/pew-report-44-percent-of-u-...
I believe you have to be a special kind of crazy not to acknowledge that as a problem. Or, considering their big user base, a very general kind of crazy.
Anecdotally I'd agree with you, but apparently statistically most facebook users are trending that way, so it's a genuine concern.
I think it means absolutely nothing. I use Facebook so I can see how my friends are doing, not to find news articles to read (unless it's an article my friend just shared, and even then only maybe). I don't think many people use facebook to get their news and nowhere else.