>This is a nerdy thing to chime in, but: that doesn't establish a causal relationship. Attractive people might simply have more self confidence, which leads to more money and success with the opposite sex.
It doesn't matter if it's causal or not, the fact that the correlation exists is enough to show "good looking people have it better".
I know I've seen an interesting study that shows that at least part of the height income gap disappears if you account for teenage height. I.e. a man who was 5'4" as a teen and 5'10" as an adult is more similar in income to someone who was 5'4" all their life than someone who was 5'10" all their life. That's hard to explain in a model where beauty at the present moment is a larger determinant of income.