There is something about the gamification of social interaction which breeds a hostile community. Power hungry users chasing internet points, or moderators needlessly raising their hammer.
I am not going to miss Stack Overflow. "Question already asked" for some hyper specific question where this is the first google result. "Not enough status" to do x/y/z (sorry, can't answer that unanswered question!), out of date answers, wrong answers being accepted as right, a right answer left high and dry.
The numbers suggest that said hostile community is actually very small, or that it never intended to contribute to the site in the first place. As opposed to Wikipedia for example, where the very hostile admins and moderators actually add a lot of content.
The “can't answer” thing is probably the reason I never contributed. I don't know the specific reasoning behind it, but it's such a self-defeating solution to whatever problem they thought they were solving.