Bathroom singer here!! There is just that good acoustic inside the bathroom that makes my voice really nice.
Who doesn't, there's always a song in the heart or in the mind. Many recognize the immediate task at hand but those who are prepared will bring added things to do. I know through a recent survey; 85 out of 100 went in, sat on the jon taking other things to do as the task was gonna take a while. Too many have a tough time leaving the smart device for that short time period outside the bathroom.
Where'r do you live? There's some crazy guy trying to sing Metallica in next appartment bathroom. He does it every evening.
Honestly who isn't? I think when you are alone and just letting loose it helps to be a little silly and let the stresses of the day seem a little less important, even if only for a moment or two.