I think the world breaks down into 2 kinds of people
People who like to eat at restaurants that require jacket and tie
and
People who don't eat at restaurants that require jacket and tie.
The former group can understand why a dress code might have benefits.
The latter group will never understand how dress code might have benefits.
I think for UA the former group is shrinking and the latter group is gaining so a dress code probably is not desireable. Despite the fact I might personally find it a benefit. I do think most people dress ok in C or F by every once in a while someone looks like they are homeless - I don't think I'll ever understand how people with enough money to fly C or F can look that bad. But they are the exception not the rule.