I wonder to what extent it also has to do with potential contributors becoming jaded. I've had a couple of experiences where carefully-made contributions on topics where I have expert knowledge were destroyed with insult by people who thought they knew better. Now, if I see an edit that should be made and is ten words, I'll make it; but if I see one that's a thousand words, I'll say "Fuck 'em, let it stay broken" where once I would have put in the time to make it right.