Well they do show government spending on IT in the graphic on the page. Also, a lot of people start civic projects for the sake of the positive feelings they get for providing civic responsibility. Kind of like why a lot of people work for non-profits for less money than they could using their skills for more commercial endeavors.

Civic duty and/or bettering government/political systems would be most apparent reason. Code for America mirrors itself to the Peace Corps, but for geeks, if that gives you any indication.

I think it just needs the right kind of people. I, for one, am very motivated by the idea of working with civic causes to help people and government connect. Subject-specific accelerators like this aren't for everyone, when compared to something like YC.