Sunshine I am a non shoes in the house wearer too...
I agree with all your reasons & I certainly find it rude when people don't take off their shoes.
To me it's also about the energy of what is collected on shoes. As you say: dog poo, cat wee, spit, etc etc. You are walking that "crap" into a home & it's actually not a good energy as well as not clean. A home is a santurary and a haven - to bring inside it this type of energy isn't a good thing IMO... I might sound wierd to some...

I have spent a lot of time studying Buddhism & shoes are routinely removed before entering a home or a Gompa. This is because largely of the pathogens that shoes collect - but also out of respect. Respect for the "cleanness" of a home or a place of worship (which a home is).

My (ex) parents in law refused to remove their shoes and I found this confronting... I find it amazing that people can just disrespect a moray in someone's home! If people ask me I say we don't wear our shoes inside. If not I don't say anything unless they are a close friend - and of course they don't wear them inside anyway as they know it's not my thing.