At least I personally am much more driven by the fun of solving problems - usually low-level of the kind - and for me having a product that works isn't particularly very rewarding. It's much more rewarding to actually come up with a clever solution to a seemingly abnormal problem. Not to say that TDD would take this away though, but I've noticed that the emphasis of problem-solving moves one step upwards to the design/architectue scale, which definitely isn't my cup of tea. TDD is meh for the most part of the really memorable challenges.

Guess what? We're all different.