What is the payoff feed readers?
 

Except the obvious?

When gathering information I suppose it makes sense but when posting information one does not automatically know another can subscribe to your feed. I didn't anyway.

If I want to visit a site I like to visit the whole site to get the whole interactive experience. I don't know why one person would want to subscribe to someones post feed unless they were a moderator.

So what are the benefits of subscribing to webpages rather than actually logging in or viewing a url directly?

I have become acutely aware of the little orange icon in my address box these days.

Its useful if you want to be aware of updates somewhere even when you aren't logged in to a given site?

If you subscribe to a thread you know when someone's posted so then you can log in to view it.