I believe the cat named Dante has been trapped thus..
I don't have a cat. I keep the doors slightly ajar, most of the time. I don't have scads of guests. I also have a very diminished sense of smell (and fairly clean ways almost because of that). In the master bedroom, aka computer haven, I often keep the bathroom lights on and the door open after dark, until I retire, for improved lighting.
As far as visiting other people's houses, a closed guest bathroom door always gives me a bit of a pause, as in, will this be a surprise?