May be based more on its integration with ipod, iphone and ipad than its overall utility with software. Incoming freshmen have unique priorities compared to days past...
I really think that Bob has an excellent point. I did a nonscientific survey of my own before buying my youngest his "graduation/off-to-college" computer. Most of the kids around here are still Mickeysoft users, by a fairly big margin. iPhones do not work in this area (I guess we are that 3% they talk about in the commercials), so the whole iToys thing just has not caught on other than iPods.