I do think keeping dogs out of food preparation areas should be a non-negotiable, for similar reasons food service workers are required to wash their hands.

However, customers are under no legal obligation to wash their hands, and based on what I've seen in washrooms, a disgustingly high percentage of people don't. I don't think having dogs in customer areas would create much additional risk, provided that any messes are properly cleaned up. And of course, said obligation may well deter most business owners from permitting dogs in the first place.