I get this question a lot. I'm betting just about every person cranking out stories is asked at some time or another why they don't "cut out the middle man" (actually, most of the editors I've met are women) and go it alone? In fact, it was the first question I answered on this blog, a year ago next week. Re-reading that, I find that even though the technology and the market have evolved, my position hasn't changed much.
In answer to a similar question, the always-brilliant John Scalzi wrote a short (and incredibly violent) play for three actors on why a writer would be insane to want a world where publishers were thrown aside in preference of a "Do it yourself" world. Check it out at his blog "Whatever".
His wife reminds me of a certain engineer I know.