Guys do because the lips are a sexual organ and because of that biting or liking your lips turn them on just so as kissing does.
i think it simply brings attention to your lips when you do it. You can bite, lick, or even run a finger or straw across your lips and it will have the same effect.
its an indication she has to restrain herself.... duh!
Probably because it can be interpreted as a clear signal of submissiveness.
If it's done properly with the whole copulatory gaze and the slightly heavy breathing, ya.
because temptation is anticipation and sublimation of pain
depends on how hard she is biting...blood and snapping teeth tends to turn some off
I really don't know why.
Yes.It is just so sexy!