Nowadays, and isn't that an old fashioned expression? a lunch attendance might involve people in stretchy leggings and droopy dreary tops, and sneakers, dressed down to the maximum degree.
That stupid plague reinforced the idea of all casual, all the time. Playing with dolls allows us to dress up and look fabulous, even if it's still day time, not to mention a vicarious experience.
Still, allowing for various interpretations of what's appropriate is freeing for some, if regrettable for others.
I wouldn't mind if an event invitation suggested a dress code. I have to figure some people just don't know. and would be grateful for a hint. Some restaurants used to have a "no jeans, no sneakers" policy, and some people resented that. I wouldn't, I'd welcome it.