[Sunflower49]

I never thought about the dog urinating in the bag-I was assuming someone who wants a bag-dog would probably make sure it got toilet opportunities but, you're right-IF it was to happen, that's a reason a shop owner wouldn't want a dog in a shop, bagged or not.
Also I'm thinking maybe if someone knows dogs aren't allowed in shops and they have one in their bag, they'll close up the bag causing the dog to be frightened and suffer...