
Thing is as long as buyers will accept such low standards there is nothing to prevent people breeding in such a shoddy way.
If all buyers insisted on health screening etc puppy farmers and casual breeders would not be able to sell their pups. this would mean they either would not breed from them in the first place or if accidents happened would have their bitches jabbed or spayed. If after that the odd unplanned litter were bred then they would work with a rescue centre to find good homes.
Rescues would have a lot fewer dogs as dogs would not be such an easily acquired commodity and less likely to be in need of rescuing, after all most would be re-homed through their breeders.