The idea is that people keep their houses clean so it wouldn't be a problem. But I see what you mean.
It's something that is very culturally significant. You don't want to bring in the uncleanliness of the outside into someone's home, its just really disrespectful. I wouldn't want someone wearing their shoes in my house

Gross.
also I totally went and deleted a post so I could post this and still be at 19,999 don't @ me