Preference.
 

How much are these types of bicycles prefered over others for students?

Besides portability and easy stowage in an apartment or dorm typical of folders, I find I can carry a surprising amount on my Brompton. The shopping basket you can get for the front holds a lot.

If you are talking about college students, I would not have wanted my son to take a brompton or any other expensive folder off to college. Dorms are notoriously insecure and theft is common inside dorms, student apartments and on most campuses. An inexpensive Dahon or other sub $300 folder makes more sense if one is going to take a folder tp campus. My son had two bikes stolen in college - one while it was chained up outside the local pub, the other while he was doing laundry and the bike was u locked to the bike rack. His roomie had his bike stolen out of the dorm room (really nice road bike).