Wow. I think its funny how everyone goes oh its so cruel to breed animals! While I do agree irresponsible people shouldn't there is NOTHING wrong breeding your animals.
There is some coat varieties that are recessive and sought after and would be much more difficult to find if responsible breeders did not do selective breeding and that goes both ways with their health.
I also don't agree with breeding any random cat UNLESS there is a specific trait you hope to be gentic. I have three cats and every one I looked online until I saw the "one" and was willing to pay a generous rehoming fee knowing its EXACTLY what I was looking for.
Kittens raised in a loving home with litters that were PLANNED, big difference, are some of the sweetest adult cats. It is very sad how many cats are strays or in shelters but its at no fault of the responsible breeders. I have adopted cats from shelters in my life as well as bought from breeders.
Also if it IS a responsible breeder chances are they have NO problem finding homes for their kittens. I had a manx cat years ago and we had two litters before she was fixed. The manxes were always the first to go and people would say how they have always wanted one and were super happy! None of them ended up in shelters! Its psychology too.
The most exotic or rarest looking kitten is usually the first to go. So of course a standard tabby cat that has an entire tabby litter will have a higher risk of not finding loving homes. That's why if you are going to breed there are many factors to concider. Be responsible. And as far as that goes all I can say is what about HUMAN population control?