One reason, which I don't see mentioned a whole lot, is that far fewer places offer a real RSS feed (complete with the article / post in question) than once did. If they offer an RSS feed at all.

I looked at aggregation options for news recently, and discovered that walled gardens and the use of custom CMS's by news organisations have made RSS aggregation of say breaking news all but impossible.

Sure, you can still get blogs, reddit, hacker news etc. But the days of essentially every website having an RSS feed are gone.