The camel pacing is based on conserving energy over long distances as well as differing terrains. Hills, woods/jungles, pastures. As to why other breeds do not have I would only be guessing by saying their natural terrains were/are more vast but singular in type. The herding dogs are from rolling hills/plains. When the Filas came to be the farms were being cut out of the jungles thus the various types of terrain. The dog had to work all of them. Back then there were not a lot of pets. Dogs performed or they did not. No one fed dogs that were not performers. S