Because neither "looks" nor "smarts" are simple real numbers that can be adjusted up and down. It's not like eye color or ear lobe size. Both are complex phenom

Because neither "looks" nor "smarts" are simple real numbers that can be adjusted up and down. It's not like eye color or ear lobe size. Both are complex phenomena with many different parameters, and there is no evidence to suggest that those myriad parameters are linked in a way to suggest worse looks lead to inherently smarter brains. The null hypothesis is that they don't and that's what we should stick with. On a more anecdotal note, I don't think inheritance is a strong factor for bad looks over many generations (which would be necessary for the kind of adjustment you're describing). Ugly parents can have beautiful children. And stupid people can have smart children, too. There is a genetic predisposition, yes, but the simple mixing of genomes over a few generations seems to be enough to sufficiently randomize a child's outlook.