I know plenty of developers, and plenty of designers. Apart from the obvious technical/creative divide, something else seems to separate the two. Developers seem far more likely to want to get involved in a project with no promises and no money. The idea of creating a product, totally unpaid, with the possibility of turning it into a business, seems to be much more appealing to developers than for designers. I know this sounds like a sweeping statement and there are exceptions, but on the whole this a common observation of mine.