I think that a large part of the reason why I don't really write large programs is purely pragmatic. For any particular thing I want done the chances are quite good that there's already some Free program or project out there that's a reasonable amount of the way there -- it's just easier to write a patch to get it to do what I want rather than start from scratch.

The other part these days is RSI, of course -- I don't generally feel that I can afford to dedicate that much keyboard time to something non-work :-(