Is this a double standard or just tradition?

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It is a very hot day. Both my co-worker and I worked for about 30 minutes doing physical labor inside a building. After that, we went our separate ways to do 3.5 hours of mostly outside work. At one point, I had to go back to the utility closet to get more paper towels. If found my co-worker sitting in a chair with his shirt off. Granted, he deserved a break due to the temperatures and humidity. I never saw him with his shirt off. It probably is very acceptable to most people for him to have his shirt off in that closet. However, if I had been sitting in that chair with my shirt off, I know he would have been shocked as would other people. It would not have been acceptable anyone's standards. Not that I want to be found that way--with my shirt off, but why is this? Is it a double standard or tradition?