it also has "occupying" part of your brain with something simple it is used to so it allows you to think of things that would be hard otherwise.

If you simply sat in a chair and starred at a wall, you don't have the same effect as being in the shower, toilet, car, on a walk, etc.

Also for many, simply sitting in a room listening to music can do this as well. It's like your brain needs to distract itself from... itself.