One big issue with online lectures is simply human error, they might be old, out of date, missing key info...I know lecturers who make a point of bulking out the in class lecture with extra material, the recorded one is bare bones basic. In class is also where you get assignment and exam hints.
Also if you haven't bothered turning up for lectures, you might find that when you need to email a lecturer, they don't bother helping, or maybe even replying, and you won't have much luck complaining if no one knows who you are. My head of program straight out said this, 'If they don't make the effort, fk em'
I personally think it's pretty arrogant to start uni and instantly decide lectures are beneath you.