A friend had a Golden Retriver and she brought a trolley from bunnings, she would lay down in it, they only went for short walks up to the canal so she (the dog) could have a swim.
I am sure elderly or injured "dunb dogs" wouldn't care what they are seen in as long as they get out with their owners. All dogs I have seen have been very intelligent, maybe you are referring to the dumb cats that tear the strollers to bits.