I don't think anyone actually bites their lip I think they are just lazy to say biting your lip skin? Or maybe people do bite their lips?? Well when I was small whenever I would feel a piece of skin hanging I would try to bite it off, or grind my teeth together to 'cut it off.' This would be less painful and feel more comfortable than actually peeling the skin off with your hands. I remember during elementary school when kids would bite their nails, I would be biting my lip skin lol.
Oh ya, b4byfac3, I'm the same as you. It's annoying when the skin grows at different rates or maybe dies at different rates I should say. That was another thing that probably screwed up people with EC even more, you try to make all parts look equal lol so you go and peel the other sides/areas.