Sunshine -
I don't know the statistics on the numbers, but a good amount of pet stores get their pups from puppymills. They often have very nice names, like Shadygrove Breeders or something like that...but they are puppymills. And I'm not talking about pet stores that have dogs from rescues. Totally different ball game there. I have no problem with that.
And here's the thing...we have two dogs. One from a great breeder (an Ibizan hound), the other from a great rescue (a muttskie we like to call an Ibizan hound knockoff). Both the breeder and the rescue wanted to meet and interview us. They called references. They wanted to make sure that their animal was going to a good, stable home.
Before we got our Ibizan, We met his mother, saw where she lived, where she slept and how amazingly well taken care of she was. We talked to the breeder to make sure an Ibizan was a good fit for us. We talked about why she decided to breed Ibizans. We got tons of great information. If you are getting a purebred dog, that is info you definitely want to have an simply do not have access to if you get a dog from a pet store.
A pet store - well, they have no IDEA who is buying that dog and what they plan to do with it. If you've got the money, you've got the dog. It shows a real callousness towards the animals, in my view.
But I totally see your point. It is very easy in the abstract to say just stop buying puppies from pet stores...but it is totally different when you think about the fact that puppies might be euthenized if they aren't sold. I guess you have to weigh that against the dogs that are currently living in deplorable conditions in the puppymills and the future puppies that won't have to be subjected to it. I don't know. It is a tough call.
eta: and of course the folks that abuse animals are awful. But not all dogs at shelters are abused. Most often, dogs end up in shelters because their owners circumstances change. And unlike the puppymillers, the person that turns an animal into a shelter doesn't get paid money for it. So I disagree that they are not as bad.