This question has sparked a lengthy discussion on the HETL group on LinkedIn. I mounted a spirited defense in the negative.
Best line I’ve heard?
Well, as a colleague (Pres. of University of Phoenix Online) noted: “If bums on seats are the major concern for assessing tertiary education, then they are focusing on the wrong end of the student!”
by David Albrecht
Pondering the Classroom 
I think, while it shouldn’t be mandatory, it should factor into the pass/fail of the student. While not everything you learn is during a lecture, it shows a poor commitment to self improvement if a student doesn’t commit to attending class, even when they don’t feel like it.