Of course many years before that it was impolite to NOT wear a cap. You were not a decent woman if your head was uncovered in public. It also meant that your hair didn't get so dirty.
After a very hot and sweaty first half of a soccer game two weeks ago I removed my t-shirt. I sat in full view of the rest of my team (all women), our male coach, two male referees and assorted spectators. I was fetchingly and sexily attired in a lime-green and black opaque sports bra, black soccer shorts, cleats and red soccer socks covering shin pads. It helped to make me feel cooler for a few minutes and would have been impossible a few years ago.
Good manners are useful for easing relations between people. Getting tense about what others are or are not wearing doesn't seem to ease relations although, on the other hand, having a common ground of accepted behaviours will help. That common ground is shifting and things are changing again. Smile and talk to people instead of worrying about their clothes.