so no shirt and shoes is a health issue, so every business has that option.
I doubt it; I think it's just a tradition, to keep eating places a little more uptown. Like those signs on country bars: NO COLORS. People can get away with a lot of stupid rules they invent---cutting people's ties off, and so on, like a restaurant I once went to in Phoenix. Until they can't anymore. Because people start objecting.
Come to think of it, MAGA hats might be something like wearing gang colors in a bar...…...the argument could be made, maybe.