Depends on the subject. For example, one of our modules is assessed with a 3000 word essay out of a chosen 7 topics which they'll release today, the catch being that each lecture was just a 'flavour' lecture to give you some background info for one of the topics.
That said, I don't think having a one hour lecture on water resources is going to help me make a great 3000-word water resources essay, so it's pointless as hell.
Anyway, in the sciences and arts it does seem to be a common thing to skip more lectures than usual, either because:
a) the content is complex and covered very rapidly, making it hard to follow and ultimately absorb any material (more common for scientists)
b) the content is irrelevant to you or simply does not or will not improve your perspective on the topic (more common for arts students).
I feel sorry for the people who have monotonous, powerpoint-loving lecturers, though, because lectures are a fantastic way to learn the material sometimes - lecturers can explain concepts or ideas very coherently, and tend to emphasise points that are relevant to the module (and ultimately your grade). I do have one lecturer who is sort of like that, but she does sound interested in her subject (sedimentology) and makes very clear and organised lecture notes.