People's irresponsible behavior is what drives this issue. People are often very appearance-oriented when it comes to animals, so if they are unable to find the look/style they'd prefer after viewing shelter animals (if they even do that), they will simply head to a breeder to get exactly what they want. Here, an irresponsible breeder will give the customer exactly what they want without any additional screening, and we have the beginning of a disaster. Perhaps the owner will be mindful enough to realize their new dog is a living creature that requires care, and they'll work to provide that care. However, if the owner bought the animal purely for looks, what's more likely is they will get rid of the animal whenever it becomes too much of a "nuisance." And so the poor dog is dumped somewhere else, and the cycle continues. Both parties are in the wrong with their actions here - the breeder carelessly pawning dogs off for profit, and the owner being negligent with the dog they just had to have.
Far too many people get their dogs from breeders. Yes, there are legitimate reasons that you may require a certain type of dog (allergies, for instance), but plenty of people do it for insignificant reasons. As I stated above, appearance is a common one. I find this extremely sad because appearance should not play a huge role in choosing an animal to add to your family. If you’re superficial enough to reject shelter dogs in favor of purebreds because you want to maintain a certain look, then you probably should not have a dog at all.
Another common issue is the assumption that a purebred dog will have the owner’s desired traits due to the breed’s temperament, making purebreds less of a gamble. This is rather silly because valued traits like loyalty or friendliness are not exclusive to purebred dogs, and it's unwise to assume those traits are guaranteed simply because of breed. Both genetics and environment play a role in their development, so breed does not guarantee much in terms of personality. Additionally, good shelters are happy to help you find the personality you’re looking for in a dog, along with alone time to see if you’re a good match.
In general, people need to adjust their attitudes when it comes to shelter dogs. Some people view them as damaged goods. Others don’t want to put in the extra effort of going to more than one shelter to see if there’s a dog that’s right for them. If we want to help curb the population problem, we need to resolve this poor attitude. We also need people on all sides to make responsible choices. Breeders need to ensure their dogs are going to the right homes. This is an absolute necessity if you are going to engage in breeding and selling of living creatures. And owners need to choose a dog responsibly – not solely based on appearance or preconceived notions about a breed. All of these would help with our problematic dog population. Spaying/neutering is a whole separate issue to tackle.