it doesn't matter that it wasn't that popular amongst the general public, they should have viewed it as having an enthusiastic user base and since sharing and commenting was part of reader, would be a way to encourage people to add content to google+. A social network is only as valuable as the content that gets placed on it. Killing reader shut off a mechanisms for sharing. I went from sharing articles I saw on RSS feeds via reader to a group of friends to sharing them on facebook.
I miss the leisure of just clicking a button to flag "hey look at this" and having a backlog queue of things by friends also thought was interesting. Nothing has really come around and recreated that simplicity and UX.