Droppings, poo, shit, faeces, excreta, stools, crap&
it's all quite natural
but if there are germs in it
then it pays to be clean.
No one I know has rats in her house.
But a few hundred years ago
most people had rats in their houses
as well as a lot of other unpleasant things.
People didn't know that you could get diseases from rats.
So if there were a lot of rat droppings about
(especially in people's food that the rats had got to)
then it could end up being eaten by people
and they would get sick.