The gestation in a dog is much longer, not to mention the litter yields exponentially less than a rabbit or other such lower animal... it's much more feasible to feed a rabbit or rat or some other type of animal. Not to mention a dog will reproduce maybe twice a year on average while rabbits or other lower rodents can do so 6+ times... Rabbits can get pregnant the day following the delivery of their litters.

Not to mention rabbits and lower animals have been domesticated for much less time than dogs. Domesticated dogs rely on us to some degree, and their intention has rarely been for food in the western world.

It could be true that someone does this but they are perhaps uneducated owners, have little access to supplies or information, perhaps are cruel, yotta yotta. We all know this isn't a common occurrence and it wouldn't be our first choice.