Why do people close the bathroom door, even though they are home alone?
Do you close the bathroom door while you are alone in the house?
I'm going to say now that this was a request... I didn't think about making a Hub about such a good topic myself!
There are several answers to this, one being that people do it simply out of habit. Perhaps a person lives with several other people, such as siblings or grandparents. They have probably had to close the door to the bathroom for years, and it's become a routine. Going to the bathroom in public places encourages door-shutting as well. Children may watch their parents do it over and over again until it becomes a learned behavior. As soon as they walk in the restroom, they shut the door, whether they are home alone or not.
Shutting the door may also be for one's own peace of mind, like for feeling safe and protected. For instance, my mom says even if the weather is extremely warm, she has to at least keep some bedsheet over her feet while she sleeps for the feelings of security. Similarly, people may want to keep the door shut to the bathroom for one last shred of protection from invaders or other dangers... or uninvited guests. Maybe they're doing something they don't want anyone to know about, so they keep the door shut just in case. A bad experience with an unexpected encounter would certainly inspire someone to remember to shut the door no matter what.
It might depend on where the bathroom is in the house; if it's a little thing attached to the bedroom at the back of the house, then people might not feel it is as urgent to shut the door, but if it's near the front of the house by the front window, that's another story...
Maybe people shut the bathroom door because they have pets. They sometimes just don't understand what a person is doing in there in the first place, so they see no reason why they can't visit.
It might be nice to keep the door shut while taking a shower so cold air doesn't come in and the warmth escapes.
Finally, they may have stunk up the room so badly that they don't want it to spread to the rest of the house.