you will remember your notes better if you write them on paper

Good point. I knew that, but forgot about it (probably since that's not my reason). They'll probably also be easier to browse and review if I care to.

I didn't used to take notes either. The main conscious reason I do it now is that I know I'm inclined to do something with my hands while in class--doodling, writing something unrelated, even crocheting or embroidery sometimes. All of these activities take some of my attention away from the instructor. If I take notes, I satisfy the urge to keep my hands busy, and also pay more attention instead of less.

(That, and I'm getting paid to take notes in one of my classes, and I would've felt silly if that was the only one I took notes for.)