I skipped a lot (okay, most) classes during my time in college. It didn't really have much to do with the teacher -- I was just lazy and would rather sleep / write code. It's not necessarily a lack of faith as much as it is a lack of ambition, in some (many?) cases. Sometimes I would take courses where they were teaching topics where there effectively were no gaps in my knowledge. That didn't make them poor professors, either, it just meant I shouldn't have been made to take the course.

If anything, I would think consistently low grades would be worse. This means that people are attending the class, but not "getting it". I think it's trickier with programming; I met many people in my programming courses who just flat out couldn't understand the basic concepts, despite paying attention, taking copious notes, and spending hours studying.