In common sayings, there is one that goes, "Marry a wife for virtue, take a concubine for beauty," leading many to the misconception that the uglier are more virtuous while the beautiful are the opposite.
However, in reality, the uglier often act out more, while those who are beautiful are more likely to have virtuous and pleasant dispositions.
Because the ugly receive less affection from a young age, and the beautiful are constantly in such an environment, it's obvious which is more likely to develop a better character under these two starkly different conditions.
Why is the notion of a femme fatale so ingrained in people's hearts?
Because those who are beautiful are more easily remembered...
Don't believe me? Just look around on the streets, are there more shrewish women or femme fatales?