By the way, it is because I agree with Teri that the concept of using animals is wrong, well, at least, wrong for me, that I don't believe in owning pets. Even if the pets are well treated, not harmed -- people own pets because of the "joy" that pets bring them. They are using pets to get joy.
People commonly don't give the animals an opportunity to choose whether they want to be used or not. Rather, they separate young animals from their mothers, at an age that is earlier than the animals would be separated in nature, and bring up the animals in a human-created environment, thus transforming them into a very different sort of animal than that they would have been had they been brought up by their natural parents. They are transformed into animals that are suitable for living with humans, as "pets."
The closest example we have for this, with humans, is the taking or buying of certain female children from their parents, and raising them to be concubines -- companion people. Such girl children go to "concubine school" where they are trained in doing what they have to do to be concubines. This goes way beyond simply having sex with their masters. Contrary to popular belief, men that own concubines don't view their concubines only as objects to have sex with. They view them as whole people, whose purpose is to serve them with general companionship, with sex beng only one part of the array of companionship services that they perform.
This is identical to the idea of "companion animals." The only difference is that people normally don't add sex to the list of things that their animal concubines do for them. If people were sexually attracted to dogs and cats, they probably would add sex to the list of things they do with their dogs and cats. As things are, people "cuddle" and "snuggle" with their companion animals, pets. If an animal isn't suitably cuddly or snuggly -- too bad for it -- people will find another animal.
This pretext that people use, for keeping whole cultivars of animals in captivity, that they are saving the animals from death or lives of misery, is just that, a pretext. People who keep companion animals don't keep non-cuddly animals as "companion animals" any more than than men who keep concubines keep unattractive women as concubines.
The purpose of keeping concubines is to have concubines, and is not to give homeless women food and shelter; likewize, the real purpose of keeping companion animals is not to give homeless animals food and shelter, it is to have the companionship services of the animals, just exactly the same way that men who keep concubines keep them to have the companionship services of concubines.
Ever hear a man try to explain a concubine to his wife, by explaining that she was a woman who came upon hard times, through no fault of her own, and that he was simply giving her food and shelter due to charitable motivations? This explanation usually doesn't sit very well with his wife. The wife is usually suspicious. And likewize, when people tell me that they are keeping some cuddly dog or cat because otherwise it would have to live under unpleasant conditions, or would be killed -- I have the same problem with this explanation as the wife of the man with the concubine. Especially after I hear the keeper's litany of cute, adorable, things, that the animal, or concubine, just recently did.
Companion animals are of course kept for different reasons than animals that are kept for labor or special skills -- for example "draft animals" that are kept to haul loads; dogs that can detect scents that people and mechanical devices cannot detect.