I once read that when people pick at their lips, it's a form of OCD,
and well, I'm about 100% sure that I have it, so it's not really all that surprising.

I really don't know why I do it, sometimes I do it without even noticing it.
A few people have scolded me about doing it, but it's not like I have control over it. That's like trying to tell someone who washes their hands more than once to only wash them once. :|