As a small recap, we've decided that there are two types of straight-to-electrons publishing: self-publishing (author+Amazon/Smashwords/etc.=book!) and ePublisher (traditional publishing, but online).
There are benefits and drawbacks to each, one of the major issues being who does all the post-sale stuff: covers, interior, coding, marketing, royalty analysis. Etc.
If you self-publish, you do so with the understanding that "self" is the operative word. You're doing all that stuff. You're doing all this analysis. You're in control, you keep a whopping 70% of the money you make. Could be a sweet deal. But by this time, enough people have told you that Amanda Hocking is an anomaly, including Amanda Hocking, that I don't have to.
Few writers make money self-publishing. Not because self-published authors are incapable of marketing themselves or even the fact that there are millions of self-published books, although that's a factor for sure. It's because after maintaining your day job (which you should do), cooking dinner, doing the laundry, and kissing your kiddies (or, insert family member/pet here), there's no time to dedicate to the post-pub.
When people get in that situation--when they need something done but can't do it effectively themselves, they pay someone to do it. Lawyers. Hairdressers. Accountants. Literary Agents. Publishers. It's not about whether writers can do it--you can, with enough time. It's whether you should. Is it best for your career to bear the full-time job that is getting a book effectively published and marketed? Can you keep doing it?
Agents aren't "making themselves needed" as one commenter put it. As I see it, we just are needed. Not for everyone, of course--plenty of people self-publish and are happy as clams about it. In fact, we're happy for them, too. But for everyone else, for whom writing and getting published are high emotional priorities, but low practical priorities, agents are the stopgap. Aside from the front-end stuff, being the "second pair of eyes," agents' job is to shepherd the book through the rest of its life.
But, really, if agents just don't resonate with you, if you really can't see the point, don't have one. Fortunately, you don't have to anymore.