Introversion does seem to have kind of a stigma attached to it, at least here in Murrika. The problem seems to be that since most people are extroverted and like being the center of attention they assume that that's how everyone should be. I'm more of the quiet type myself and a lot of people, especially my parents, seem to see this as a negative thing.
In my French III class from last year, the teacher insisted on making class participation part of our grade. She expected everybody to be talkative and active in class and if they weren't, they'd get a low participation grade (luckily she never went through with this). A debate proceeded where some students pointed out that people shouldn't be penalized for being quiet and she still insisted that being talkative and active was the only option. Still, it was nice to see that some other students, who were more outgoing, saw that being quiet isn't bad.