That reminds me of an interesting tidbit from my youth. In elementary school, the stall doors were removed, I suppose for the same reason. Because of that, nobody ever used them. You just had to hold it. One day, I just had to go. One of my wonderful classmates walked in on me in there, and I was mercilessly mocked for quite a while afterwords. Good times.

The "open" design makes sense in schools in my opinion, but not really in, e.g., a professional environment.

At least in a professional environment nobody would mock you. School is already full of social awkwardness. Do we need to make that even worse to the point where you can't even go to the bathroom in piece? If a kid wants to smoke they'll find a way anyways and they won't die from it either. I find removal of bathroom doors inhumane.