I think a lot of characteristics that many people call "superficial" are actually good indicators of other traits and habits that are NOT so superficial. And here's why:
To paraphrase something I heard a comedian say once: "Follow a fat, lazy kid home, knock on the door, and I PROMISE you a fat, lazy parent will answer the door." I've tested this rule, even though it was meant as a joke....It's not.
I don't say this to offend anyone, but in my 33 years of experience, I've found that physical fitness, good hygeine, grooming, and just caring about one's overall appearance, demeanor and first impressions, or a demonstrated lack of these traits, have been pretty reliable indicators of a person's motivation, self-image, work ethic, social skills, etc.... Or a corresponding lack therof.
Of course there's always exceptions and unforseen circumstances. But as a rule, I've learned that what you see is most often what you get.
I believe there is a scientific basis as well. All living creatures on this planet, in some way or another, make an effort to choose the most appealing, strongest, and physically healthy and superior mate, in order to maximize the chances of having strong, healthy, appealing offspring, thus maximizing the chances of the survival of the species. It has worked since the beginnings of life on Earth. Why should anyone think humans should be an exception to that logic?
Just my 2 cents again....
Mike