- Inertia. Just not getting around to it. Possibly a certain amount of laziness.
- Mailing lists. I had to use mailing lists at university, and I hated it. Hundreds of mostly inane emails each day to wade through. Awful. What a wholly inadequate substitute for newsgroups.
- Complexity. I started reading about contributing, and that led to the new maintainer process, and all that other documentation stuff. This is the internet age - anything requiring an attention span of more than five minutes will not be read. Remember The Big Chill: "We only have one editorial rule: You can't write anything longer than the average person can read during the average crap." (Actually I'm sure it is not really that complex - this is probably just a restatement of 1. above).
- Scale. Debian is big. Really big. Where do you start?
Recently I read somewhere that submitting bug reports is considered at contribution. I guess that's obvious, but for some reason it hadn't occured to me. I have reported bugs a couple of times! Excellent. That means I can stop feeling guilty about my lack of contributedness, and maybe go and read some ctrl-alt-del, content in the knowledge that I am not such a freeloader after all.
Browncoats: You lost. Get over it.