North Carolina passed a "religious freedom" bill just as Mississippi recently did. What is disturbing about these bills is that they allow any business owner to discriminate against anyone if they feel that serving them conflicts with their religious beliefs. That is the first part of the bill. The second part allows government employees to deny service to anyone if it conflicts with their religious beliefs.
So why do we still have separate "gang" restrooms today? This goes back in time to earlier years when the cost of plumbing and construction was much higher. When I was in High School, we had "gang showers" - large tiled rooms with dozens of faucets. It was cheaper to build, I guess, but there was no privacy and a lot of towel-snapping going on (plus leering gym teachers). Today, most modern high schools have separate stall showers, as do most health clubs and other athletic venues.
1. It is gender neutral in that women don't have to wait in separate lines.
2. If there is a maintenance issue, you can close one of a number of such restrooms with little or no impact. If you close the men's room or the ladies' room, you have to get porta-potties for one gender to use until repairs are effected.
3. For families with small children, the single-occupant restroom is a godsend.
4. All of them can be made handicapped accessible, so the handicapped don't have to wait for "the" stall or be stigmatized.