In the latest years there have been a complete women lip buzz. Larger is better seems to be the guiding principle. But why? well, according to Wikipedia :
The lips are a sensuality sumbol. Ther are a tactile organ and has a plesant soft feeling. Some people argue that the reason is that the lops mimic the look of the labia of the vulva. The lips are therefore a secondary sex characteristic. (You remember good old Sigmund Freud, don’t you?)