A lot of students probably shouldn't get their cards while in college due to the fact that, well, colleges are drug free zones and weed is still considered a "drug" --medical or not. Also, a lot of students use FAFSA (FEDERAL aide) so you think that the Federal government is going to loan money to a Medical card holder?
Not to say that there aren't students that get their card while in school, I had a couple buddies in college that had theirs, but it isn't too common and it would probably be best to wait until after graduation.