[CuriouslyC]

To expand upon this, even if something will make the lives of others easier or could be a profitable product, that's still probably not worth doing since once you've built the thing you still have to market it, which is frustrating if you're not the sort of person who's into that (and then you probably wouldn't be a developer). There are a lot of excellent things (software, art, music, games, etc) that end up languishing in obscurity because they didn't get marketed correctly or enough, and that can be incredibly frustrating.