Anecdote I remember reading from many years back (so sorry, I can’t give a cite): There was a large ranch in far north-east California, where the population density is in the neighborhood of 1 person / county. And a ranch house on the ranch, where one ranch hand lived.
So a Cal-OSHA inspector showed up one day, and cited the place because there was only one bathroom in the house, and not two separate bathrooms, one M and one F.
The rule was, in those ancient benighted times, that there MUST be separate bathrooms for males and females, and a single single-use bathroom was not good enough. The logic seemed to be to protect people (mostly females, I suspect) from picking up cooties from the toilet after it was used by the opposite sex.
So this would have required a big change in attitudes about public health to allow a single-use bathroom to be used by males and females as is common today. We now seem to understand that the cooties you can pick up from toilet seats are completely pan-gender.