In my experience, the problem isn't limited to geeks. People in general don't organize politically.
Why? I believe it is because they don't understand power. Some fear it. Some consider it somehow immoral (we are all taught that repeatedly). Some don't want the responsibility that comes with it.
An understanding of the nature of power is absolutely critical to effective organizing but it is not the only thing. The ability to identify mutual self-interests and to actually care about the other person growing in public life is also necessary. None of these things demands an extroverted personality.
Organizing is HARD and takes a boatload of patience. It is not a way to quick victory. But it is the way to longstanding victory.