I think it might be because lighter skin allows facial features to stand out more, and I was reading a piece on how female attractiveness is generally associated with child-like facial features and expressions (big eyes, big smile) that become more pronounced on lighter-skinned women.
In my experience, though, Black women tend to run the gamut from broke as fuck to fine, and mixed women tend to be either 10s or 0s...like theres no inbetween with mixed broads...they are either like GOD DAMN shes fine or FUCK shes hurt!
lol