I've been thinking about this. Having to prevent being observed is not without cost and many time is inconvenience and annoying. Why do I even need the door closed in the first place ? Because other people will I think I'm weird ? Is it cultural thing? Why do I have to feel embarrassed/ashamed when people see me in the bathroom ? What if as the society changes to become more open, the more people leave the door open, the more it become the norm, then I don't even need to care anymore whether the door is open or close when I'm using the bathroom.