Ask HN: Is Twitter non-existent among my age group?

I am in my late teens and currently going to college. None of my friends either at my college or friends from home who go to other colleges use twitter. Those latter friends at the same time don't know anyone else who uses it. I've come up with a hypothesis that maybe Twitter is mostly popular among people who have already started professional careers. Is this correct?

Otherwise, it amuses me that so many people, especially corporations, view Twitter as the "cool" thing to do and that all the "young" people are doing it. If anything, seeing someone promote Twittering has the opposite effect on those I know. So I'd like to ask HN if they have any clues to this, why is it that Twitter is huge on the Internet, but rarely spoken of among people I know?