They do not only close, they also open.
They limit access and thus create mystery. Without them, curiosity would be stumped.
They give a sense of home--NGO research states that in refugee emergencies, even just a cardboard door is a significant psychological improvement over the open-walled tarp-ceiling setup.
They are fundamental to an adolescent's healthy development, a good way to mark territory without using bodily fluids.
They translate well into the digital realm, making liminal spaces even more effective and immersive.
Elena, you guessed my secret: as a child, I never had my own room...