I've also had it pointed out to me that writers don't need agents to get published. This is true. That said, I need an agent. And here's a little hypothetical scenario to show you why:
Publishing House: O hai there! We love your story about a beagle who's secretly a ninja, fighting to save the world, and we'd like to offer you a two-book deal.
Me: Oh wow oh wow oh wow! Where do I sign?
Publishing House: Here, you can use this bottle of red ink. Just sign on the dotted line.
Me: Wait a minute. That's not ink, that's blood! And Paragraph 18(b), right under the part about electronic rights, says I'm selling my soul! And there's nothing in here about payment.
Publishing House: We're glad that you asked about payment. In return for us giving you a two-book deal, we are prepared to give you this here Slurpee, cold and refreshing, along with this piece of string and a brand new paper clip.
Me: Paper clip. Oooh, shiny. (bats at the paper clip, taking a sip of the Slurpee) Deal!