It doesn't sound like it's an all campus thing, it sounds like this girl is saying THEY don't do it because they think it's tacky but all the other (tacky) sororities do and therefore they're better than the other sororities.
I can understand not wearing letter sweatshirts someplace like shinerbock's campus where it doesn't get under 60 degrees - sweating like a hog when you don't have to is always tacky.