Universities can study porn under the heading of the humanities or social science. The fact they don't have an explicit "Department of Pornography" is both an accident of our culture and a reflection of the fact our "top-level categories" for academics are more abstract than that.
My point is, libraries maintain a very curated collection, and choose their holdings and resources based on very restrictive criteria, including funding and shelf space, making them relatively poor at keeping broad and deep holdings. Until you give the library an Internet connection, which brings us back to the origin of this sub-thread.
It might be a difference, but it's a difference for which the university comparison is a red herring.
How many universities have a porn department?