No clue. But it's hot.
Why do people bite their lip?
Most probably do that if they're nervous, or out of habit.
Several reasons:
-Sign of thinking (Some people do it automatically while they are thinking deeply)
-Sign of stress & fear (some people do it automatically in stress times just like tabbing foots on the ground ect . . )
-People also do that for posing in shooting pictures ect . .
-Just a wrong habit (some people do that as they don't know why or how it happened, they just got used to doing it!)
-Some people doing it for gaining focus (just like chewing gum which gives some people focus ect. . .)
-Some people do it automatically during intercourse for releasing their emotions.
-Some people do it for emptying their anger at the moment so they don't ignite their anger out.
-Some people also do it caused by psychological disorders.
ect . . .
I think it's hot too. Lol.
I bite my lip when I'm bored :p
I use to bite my lip and that was when I use to get in to trouble. I grew out of that habit.