The sales of their dogs are supporting the unreputable breeders that the dogs come from. It is never a good idea to purchase a dog through a pet shop, with the exception of the dog being a fostered rescue dog, and even then its likely the purchase would be through the shelter, not the pet shop. If you want a puppy of a particular breed, find a reputable breeder. Here's a hint, you'll be on a waiting list to get your dog, because it will be an experience worth waiting for. Don't support puppy mills.
Just because the dog is healthy doesn't mean that it's poor mother isn't being treated like crap at the hands of a poor breeder. Good breeders do not even need to advertise, as people come to them looking for puppies who are bred in a good environment. Good breeders do not breed until their is a demand for all of the puppies who will be produced in their litter. They do not let their dogs suffer, and have no need for them to be put on display at at pet shop... it just isn't acceptable to a good breeder.
I wouldn't even sugest buying pet supplies here, why hand your money over to a place that supports cruel treatment of dogs (and people's children from other reviews I've read) when there are plenty of places in the area that do not. For pete's sake... buy at target before giving money to someone that allows the mistreatment of animals.
Just because a dog purchased from a pet shop is healthy, well behaved, and the love of your life does not mean that its parents aren't still subjected to abuse at a puppy mill somewhere. Sure, your dog is loved and well taken care of but the dogs still at the puppy mill have a different story to tell, and buying from bad breeders does nothing but give them money to continue their immoral business.