Except the only people who want to be darker are largely white people, and lighter is pretty much everywhere else in the world where's there's people of color. It could be simply that they want to look like they don't have to do hard labor for a living, which is where the preference started or it could be something more.
Well duh.
The hard labor argument has absolutely nothing to do with it, of that I am sure. Nobody thinks they should be darker or lighter so they don't get confused for labor workers.
It's all just a desire to look unique or "exotic" compared to what people are surrounded with. The human desire to feel unique is not unique.