I work in a retail environment that stocks a wide range of outdoors and pet products and so regularly see dogs both service and otherwise wandering around the store with their owners. As I work on the shop floor I often get first-hand experience watching how these dogs behave whilst their owners are shopping.
There are a couple of regular service animals that come in to the shop these include a couple of hearing dogs and a guide dog. I'd go as far as to say that it is brilliant to watch them work. The amount of training that goes into these dogs means they have come into contact with so many of the distractions that are present in a shopping environment that they are focused on their owners completely. They never bark, there are never any accidents, they don't jump up and they walk nicely next to their owners. They also nearly always look relaxed. In other words they have been socialised during their early years to accept the numerous stimulus and objects that appear when they are out and about. This is something that we might not even think about when we take our dogs out to a new environment. A walk down the road to a local field is going to have different distractions and stimulus compared to a store full of strange people and smells. The problems arise when a dog is thrown into a completely new environment surrounded by objects, people, sights and sounds he has never come into contact before.
(Walks down the country lane have different sights, sounds and smells compared to a retail environment)