I think for a lot of people it's a comfort thing... I just switched to the Pro Staff 90 after several demo sessions... and while it took a few minutes to get used to, I think I've been converted(for now) to team mid. I used to rock the Juice pro, which is a fine racquet but was too powerful for me (also lacked feel, but that's a whole different story...)
Most players I see in college tennis (and saw in HS) used lighter racquets with larger headsizes (Babolat aero pro and pure drive) because it was what they were used to. Some might not have had the physical tools to play with more of a "player's" frame and not see a drop off in performance. Others just seem to never consider it. I tried one on a whim and really liked it, and now here I am playing with one of the most "player's" frames on the market. So I think some people don't really think about trying one, and others are scared simply because of what they are used to.