I think of it this way: If the only thing these owners did wrong was own a dangerous dog breed, then you’re not going to get a conviction, unless you make that a crime.
You're missing the point (I suspect deliberately) - there have to be TWO conditions if your pit bull attacks someone - owning a dangerous breed and failing to control it.
If you leave the parking brake off and your car rolls over someone you are usually charged for negligent homicide. If you don't have a fence around your pool and a kid drowns you are charged. It is not illegal to own a car or a pool, but you are charged anyway because you didn't take the proper actions the protect others from your car/pool. Likewise if your dog attacks someone, then you obviously have failed to control the animal