But you're going entirely on the assumption that a class is necessarily ONLY about aquiring information, but not applying that information and displaying competency in the area the class covers in other ways. While there are indeed many classes where that assumption would be valid, there are nearly as many where it would not. We also have to do presentations, and watch other people's presentations because they need an audience to get anything out of the experience. I'm an art ed. major, and art lab classes absolutly need mandatory class time - and weekend time to fire the kilns, and studio cleaning time, and critiques, etc. There's a name for classes you don't regularly attend; it's independent study.
Personally, I consider it to be very valid, and even a good idea for a professor to include questions in the test that were covored in class time only, and are not in the textbook, as some of mine have done.
If college were only about information for tests, I would be at home reading a book, not at college.
EDIT: and a bad flue is generally considered a valid excuse, and not counted against you. Except sometimes, when it's really important - I had to go to final critique and an essay test with a flue, but I really did survive the experience, because it was essential to the class.