They did have comments and other social elements [0]. It was possible to follow people and share articles with or without adding your own note to it. They had a bookmarklet that allowed you to share any article, even if it didn't have an RSS feed. Their move to Google+ sharing wasn't exactly an improvement though [1].

I never got why people moved to Twitter, it wasn't, and isn't, as good at consuming or sharing content as Reader was. It's just one more step towards the more centralized web we have today, and hopefully we will move back to a more decentralized experience soon.

[0] http://googlereader.blogspot.se/2009/03/google-reader-is-you... [1] http://googlereader.blogspot.se/2011/10/new-in-reader-fresh-...