I don't allow people to walk around my house wearing shoes. When I get home I wipe the soles and edges of shoes clean before they get put away. I'd never go outside in slippers.
People spit, puke, wee and do God knows what else on the pavement not to mention what animals do and flick their leftover smoking paraphernalia on the floor.(Not animals for the last one)
I won't put bags on the ground at bus stops or train stations because of this either. I balance them on my knee and just hang on to them if waiting for public transport.
I'm told I'm odd, does anyone else do this? I don't want remnants of piss and puke, old pizzas and other stuff brought into the house.