Mandatory attendance makes sense to me. It's kind of like writing papers or doing mandatory assignments: these things don't necessarily teach you anything, improve your knowledge, or measure your competency, but in general, for most students, they help. Take jeffd: he is (I gather) in an English course where he is required to write papers which don't teach him much or improve his writing. If he decided not to write those papers his grades would suffer. That's not unfair, even though for him those papers have little educational value. I think it would be kind of unfair if students could pick and choose which of their obligations they will meet based on their subjective feelings about the value of lectures, assignments, and tests.