We don't like to acknowledge that we judge people by their looks and dish out different treatments based on it, because it's admitting that we're shallow assholes.
We'd rather blame our mistreatment of unattractive people on their "bad personalities."
That way, we're not the bad guys, it's just a defense mechanism against their so-called bad personalities.
Which is a total cop-out/rationalization.
Truth is we perceive attractive people to have good personalities, even when they actually don't.
And vice-versa, obviously.
An ugly guy who's confident will be accused of being "cocky," "uppity," "faking it," "try-hard," etc.
A hot guy who's confident will be perceived as, well, exuding true confidence.
But guess what?
It's the exact same personality trait, just expressed by different people.