If it is possible to put bags on the dog, then why not hang it on the back and use it instead of other bags? What's the meaning of this option? A lot of weapons need to be held in two hands, and with a firearm ORGM is impossible.
With the introduction of cars, dogs could be the best and easiest substitute for carrying Luggage, but because of the inability to place a sort of "container" to give bags generally do not make sense