Why exactly does 'looking good' work?

[caspex]

Looking good can make social interactions much smoother and many times helps you get stuff done quicker. I think we all know the gist of the benefits. My question is, why? Is it all the health and fertility indicators that tricks are monkey brains into favoring this person or is there more of a psychological role? I get that a good physique, at least for men, shows that this person, despite all his personality traits, has some sort of consistency and ability to put in the work. One example I think about is Simmons in Whiplash. 

Think about it, as you watch the movie, you sort of hate the guy but there's also an understanding of why he does it that way.  People who watch that movie typically don't tend to describe Simmon's character as hypocritical upon first watch. But I believe that the story would change if he was fat and unfit. Suddenly, for most people, the emotions would flip. At least I would have seen all his demands and precision as hypocritical. I'd feel this subconsciously, but it'd be there. The presence of a bad physique would show to me the absolute lack of discipline and self-control this person has, and the fact that he demands such precision from others would be very hypocritical. If he was neither fit nor unfit, but average, this feeling wouldn't be quite strong, but it'd be somewhere in the middle, and being fit definitely helped his case.
 

But that's a very easy example. What about good facial structure, a good frame, being tall and other genetic lotteries? We understand that those features do not require any inner work to achieve, it's handed to you from birth. But people still get 'tricked' by it, if you know what I mean. I understand that evolutionary speaking being taller and having a bigger frame gets you more reach in fighting situations and it also indicates that the person was well-fed and under good conditions, but what does a person, subjectively, feel and really think that attracts them?

I think it's also important to note that I am asking these from the context of your everyday normal and social life and person. For a spiritual guru, attractiveness stops mattering as much and I actually think an attractive spiritual guru can be quite the hindrance. Spirituality is really working against all the survival programming so that checks out.

[LordFall]

Because you're an biological machine mostly made to fuck and reproduce mate and beautiful people around you are a proof that your tribe is successful at reproduction and you have high quality mates available to you. 

You're much better looking at it from a sociology/anthropology angle than just good looks, it's such a limited view of the world. Go to any popular restaurant in your city and see some beautiful people working for minimum wage, they haven't made it quite to the top of the social hierarchy yet. 

[Ramasta9]

Feeling good = looking good

that's the paradox.

[Joseph Maynor]

Sometimes your strengths become your greatest weaknesses ironically.