RSS feeds simply return the last N posts, correct? How can RSS be used to serve a user's whole history?

Already, we talking about some other service that accumulates the history and provides search, history, etc. That and many other things (likes, replies, quotes, etc) are all things users expect (rightfully, IMHO).

While orgs/people simply issuing announcements should ideally provide an RSS feed, that type of content is a tiny part of "social media".