Kanazawa and Still (2018) showed that very unattractive workers earned more than unattractive workers, sometimes more than average-looking or attractive workers, because they had higher levels of intelligence and education.

Very unattractive people have exceptionally low personality trait 'openness' and hence less likely to suffer distractions. They also have high levels of passion trait 'grit'

Sauce: https://www.sciencedirect.com/science/article/abs/pii/S1570677X17302204