Females are bred ever heat cycle until they are worn out and then they are sentenced to death. The horror of puppy mills is encouraged every time a puppy is bought from a puppy store. The main reason is that responsible breeders will not sell puppies to pet stores. Good breeders want to make sure that their puppy goes to a good home and is well cared for. They want to be actively involved in screening the home that their puppy is going to.
Breeders are also concerned about keeping track of their puppies that they produce.
They want to know about any health problems that their lines may carry. A pet store generally never hears about their puppies once they leave the store, and really don't care. Once you take the puppy home from the pet store they do not care what happens to the puppy. They do not care if the dog is left to run loose and kill livestock, or if it dies of liver disease at one year old. If you have a training problem they will not give you training advice.