The initial thought behind it was we didn't want to disappoint organizers (campaign creators) by implying we had a market that was going to buy their design. We also didn't have that many cool campaigns up and running at any one time, and didn't know if that would impact user's perception of us.

As we've grown that has definitely changed, and we're in the midst of a redesign that adds a discovery portion to our website!

Here's an early WIP mockup showing the new discover functionality: http://i.imgur.com/2Khj2A6.jpg