I can see the appeal of it and all, I know my dog prefers to go places with me rather than stay at home even if we're only going to run errands and she stays in the car with one of us while someone goes in a store. Before my brother moved out of state, we used to walk my dogs together and stop at the produce store or Dunkin Donuts fairly often, with one person waiting with the dogs while the other went inside. In fact we used to go to Dunkin Donuts so often, like up to a few times a week, that the guy that owned it started spontaneously giving us a bag of donuts "for the doggies" whenever we came in.
Basically the slightly older donuts because they'd make fresh ones all the time. Of course I only would give the dogs some small pieces, donuts aren't really a healthy snack for them heh (especially since my dogs were usually on a grain free diet!) Even though they only got a taste, the dogs would get excited whenever we got near that place!
I guess it's not just that one location either because we went to a different Dunkin Donuts once with my brother and the dogs waiting outside, and the guy behind the counter noticed the dogs and did the same thing. Dunkin Donuts are really common around here. My brother and I used to joke that if we'd wanted to we could walk the dogs to a different Dunkin Donuts for every day of the week, that's how many there are in the area. I kinda wondered if they do that a lot, if there are some dogs in the neighborhood living off Dunkin Donuts though, or what. 
They also opened an Oberweis in my neighborhood a few years go so we'd walk the dogs there sometimes too in the nicer weather, but they have a walk-up window so you don't even have to go in to get something...