How do you know people won't want it unless it's built? I understand not doing it if you're offered equity and you think the idea sucks, but if you're just being paid to develop a site, even if its a bad idea, why do people refuse that? This sounds like graphic designers I know who refuse clients because the client wants something ugly.

Because staying away from what looks like a bad client is a good way to keep your sanity.

The point is that the reason that it's worth anything is one of the greyed out areas. All they really give you is the genre.