Well, breeders do supply pet shops with the animals... sometimes. Other times the animals may be wild caught. Assuming a breeder can produce and sell offspring shows that the animals are being given the proper environment, food, etc. Many of the 'leftovers' (what a horrible thing to call them), aren't taken care of as well by the pet shops, (employees aren't knowledgable). Therefore, the animals in a pet shop are more likely to come with associated problems. It just makes sense to buy from a breeder if you want a quality animal that is not going to have a whole lot of complications.