With Google Reader Gone, Facebook and Twitter essentially have taken the place of feed readers. It makes a lot of sense for Facebook, it's not merely a social network anymore. It's acting like a social 'OS' for the users now.
Yahoo.com used to be that "social OS" in the 1990s and early 2000s, and look at them now. They even had a Facebook-like feature as part of their service, Yahoo 360.
Google Reader and RSS has outsize importance in tech and blogging circles, but as someone who was in college in the late-2000s, I count on one hand the number of people who knew what RSS even was. I'd say FB and Twitter killed forums and website comment sections.