Art school is a series of project-based classes that culminate in a portfolio of original work that the student can showcase, and that system seems to make perfect sense to everybody.

I don't know why other disciplines have been so resistant (forget textbook publishers, I mean the professors, deans, and other administrators themselves.) It's not clear to me there are any reasons to be against it, so perhaps it's simply the inertia of large, bureaucratic, conformist institutions.