There is a great deal of debate about whether anyone should ever buy a dog or whether everyone should adopt one of the millions of dogs and puppies that are euthanized each year. It would be nice if people would be willing to adopt a pet from a pound, but most people are just not willing to do this.
It would be difficult and speculative for me to try to list all of the reasons that people prefer to buy a purebred puppy from a hobby breeder over an unregistered pet from a shelter. (PLEASE DON'T EVER BUY A DOG FROM A PET STORE OR A PUPPY MILL.) It is likely very similar to the reasoning behind the vast majority of people having their own baby over adopting one that is available in need of a home. Sadly, that is human nature.
My wife and I are hobby breeders. We love our dogs. They often sleep with us, sit on the sofa with us and take walks with us. This is, sadly, not the case for way too many breeding dogs. My parents were of the philosophy that a dog should be allowed to have one litter, then it should be spayed. It was a member of the family and this is what it deserved. We would find friends and neighbor to adopt the puppies or we would raise them. This is also somewhat out of favor these days. My parents were also of the school of thought that no one should ever pay money for a dog. There were always people looking to give one away. This includes people looking to give away purebred dogs that they could no longer keep.
As I grew up, we had many random new dogs and puppies come randomly into our lives over the years. Most people do not wish to live this way now. People expect to be able to pick the breed of dog they want, with characteristics that they want, when it is convenient for them. This almost always means buying a puppy. Given this fact, we strive to do the best we can with breeding healthy and high-quality puppies from well-cared for and loved dogs.