Guys And Their Legs.
I'm not sure if this rates as a social norm or not but it is definitely something that seems to be universal amongest men in the western world...especially in rural areas.
Men. They stand around in groups at parties, meetings, field days, other social events catching up with whatever guys talk about - BIG sheds, BIG fish, BIG tractors, BIG weekends ;), BIG cars, BIG computers, BIG whatever... Have you ever noticed that the more they are try to impress one another, the further their legs part. When I'm bored at events that are male dominated, I like to stand to the side just and just observe groups of men and their legs - quite a phenomenon!
It seems that the more threatened they are feeling, by what the other bloke/s were saying, the farther their legs part, inch by inch shuffling into a stance that increase their pelvic tilt. It makes great entertainment if you are ever bored at a BBQ!