Coming back to this a year later with another question: since the animals at pet stores/animals that are bred are considered unwanted, what happens to them if people don't buy them? I often think about how unpleasant it must be for them to be in a pet store, and some facilities euthanize unwanted animals, right? I think it's just those poor animals didn't ask to be born, so I think to myself "don't they need a home too?"
My honest answer would have to be "I don't know," but your question inspired me do some typing. I have never worked for a pet store or had any involvement with the pet trade, but you can find some testimony from those who have. I also know the Internet can contain "questionable" material, but I found these threads interesting, though I can't vouch for their accuracy:
What do they do with unsold pets in pet stores?
What happens to the unsold pets when a pet shop closes?
Don't buy pet store puppies (this one argues that you shouldn't try to "rescue" puppies from pet stores)
What happens to unsold cats?
What do pet stores do with unsold animals?
So far, the threads I've found have
claimed that animal euthanasia in the pet trade is rare, though it does happen. As expected, the answer contains a big dose of "it depends." Variables such as the type of animal, the local laws, the disposition of the supplier, the situation, etc., all play into the fate of pet store animals. Some have claimed that pet stores have no trouble selling 99% of their animals. An animal's ultimate fate then seems to balance more on the ethics of purchasers. So, even if sold, an animal's troubles may have just begun. Are the purchasers buying the animal for the right reason? Is the animal seen more as "a toy?" If sold to a child, will the child's parents monitor how the child treats the animal? How will people train the animal to become an "appropriate" household member? I have personally known people to do things to their pets that I considered outright barbarous in the name of "domestication." It was shocking. I will admit to making a few careless and foolish mistakes myself in the distant past either out of lack of knowledge or sheer obliviousness, but I was also very young when these occurred. I still feel terrible about them. The things I mentioned above were done by adults who I thought should have known better, yet I considered them generally good people. But they were also doing "recommended" practices. I found the situations revolting. Given that, I often worry more about animals living in human homes than animals in pet stores.
Though I understand why people have pets, and I do live with a rescue bird, I overall don't agree with the whole concept of "pet." It does feel exploitative, unfair to the animal, and insensitive. Of course what does one do with animals bred for captivity who couldn't survive in the wild? That ship has unfortunately sailed and would take some effort to undo. So one hopes that people who acquire animals as housemates do so with the animal, and not their own entertainment or gratification, clearly in mind. Though, as I've said, I've seen perfectly decent people do things that I consider awful to their pets. So one can hope that compassion prevails.
Given the situation, supporting no-kill rescues or animal sanctuaries seem like good options.