Hi again Cindy. Again, a good question, and I guess I couldn't come up with a better example of how selfish human nature is than to use your question. I know. Why on earth would anyone want to breed their dog who isn't either a commercial breeder in it for money or a "showdog" person in it for their own ego (which they try to hide by saying they do it "for the betterment of the breed").
I have made a living off the "pet industry" for eleven years now, both as a vet tech and groomer. In that time I have met countless "casual breeders". These are people who quite often understand that we are in the middle of a pet overpopulation crisis, are often wont to say "oh I can't even go to the SPCA and look at all those poor dogs", but who nevertheless breed their dog deliberately. Why? Because they don't REALLY care. They are selfish. They are aware of a problem, but they want what they want anyways. They'll make up any excuse to justify getting what they want. Here are a few examples:
"My kids want her to have babies" A variation on the whole "miracle of birth garbage, only worse, because this time, theyre saying it's the kids who want it and they can't say no. Doesn't fly with me though.
"She's such a great dog, we just have to have one of her pups". Yeah, and all the millions of dogs on death row in pounds and SPCA's aren't just as great?
"We know there's too many animals but we already have great homes waiting for every one of the litter". And no regart for the fact that millions of dogs and cats are sitting in pounds and SPCAs waiting for those homes- and they just got taken

away by another idiot who decided to breed.
And when I point out this fact to these people you'd be amazed at how many say "Oh but these homes wouldn't want a dog unless it was one of Missy's"(or Sport's or whoever) No joke. People actually say this to me.
I think you get the picture. These are the "casual breeders". They are out there, they refuse to accept any well thought out reason for not breeding their pet, and they need to be controlled or licensed at the very least.
And me? I live for the day when there is no "pet industry". I love caring for them and working for them, but I've seen toomuch suffering. I'dgladly make a career change if it meant an end to animal suffering.
I hope this helps you understand the why's and wherefore's a little better. Unfortunately, in the bigpicture, we areasking for human nature to change. I don't hold my breathe. But thoughtful people like you who ask intelligent questions give me some hope.