Cuz we aren't all science aficionados

Girls like natural because God made it and we happened to find it and have the ability to refine it into something worth decorating ourselves with, which causes it to be treasured. The very journey it takes is why it's valued 

Man-made diamonds feel empty and cheap- oh wait, they are. Who cares that it's molecularly a diamond? If we can just make them, they lose their intrinsic value