Gosh we have a lot of prudes in this country. There really isn’t actually anything that inherently unpleasant about the human body that you have to cover it up at all times – that’s just a cultural thing. The saunas in Austria have already been mentioned – it was in Austria I experienced it, but at a selection event involving young people from a variety of European countries. All but the Brits happily stripped off everything to go in, I was the only Brit to do so, but despite my relaxed attitude to nudity ingrained cultural norms meant I still felt uncomfortable!
Unless I’m missing something, the OP isn’t talking about people doing helicopters, simply carrying out normal human social activity whilst wearing less clothes than usual. You do realise that in such circumstances it is still conventional to look somebody in the eye when talking to them, so how can you actually notice the difference from any other situation?
Maybe this is a posh gym thing where it becomes a big deal to either flaunt it or hide it. I used to regularly train at the local canoe club – we have a pretty nice building for a private sports club, but the changing rooms are all communal with no individual cubicles and communal showers. Yet we all quite happily chat to each other whilst changing – I don’t think anybody pays any attention to how little anybody is wearing. Why on earth is it such a big deal for some people?