As a UA Silver in undergrad, I had a surprising number of upgrades, most pretty short but some of them actually pretty decent like SFO-PIT and YUL-YVR (irrops).
I also splurged for a $295 buy-up EWR-HNL after I graduated.
I also knew people who had their parents buy F with miles, and I imagine some of the users here use some of their upgrade certificates on their kids. Aside from some of the loaded international students, I really don't think college students are forking out their own $ for F.