Interestingly enough, it may be women themselves due to societal expectations.

It is legal in Canada. One day me, my partner and a friend (very feminist friend) were at the park in a nice spring sunny day. I removed my T-shirt and laid on the grass. She said something like “I think is should to”. I said " go ahead, why don’t you?" and she said something about feeling uncomfortable because no one else was doing it.

(It wasn’t shyness with us. I had already seen her naked)