The lips like the eyes represent personality. Personality is expressed through speech and therefore is a reliable gauge of intelligence in your subject. Unfortunately, intelligence is not the first thing people seek out in romantic pursuits, is it?
Usually, physical attractiveness and sensuality are of greater interest to most, especially in the younger age group.
The lips reveal our ability to nurture others in loving relationships. Therefore the lips just like the eyes, give us clear insight into the sexual nature of human beings. And if the nose is considered to represent the male phallic, then the lips relate to the female sexual organ. In some systems of face reading the lips indicate the spleen.