I have to disagree. The mutts I have adopted have turned out to be one medical issue after another while my purebreds bought from quality breeders after much research have been nearly issue free.
Anyway, I do agree that there are plenty of SHELTER dogs (purebreds end up in shelters too) who need homes.
When you hear of a friend of family member talking about getting a new dog, you can always suggest going to a local shelter. If they already have their hearts set on a specific breed, look up some nearby breed rescues. For example, I have a Smooth Collie. I love the breed. I am not open to another dog right now as I am only allowed 2 (I have a Bluetick Coonhound pup) where I live. I was flipping through the shelter dogs and what do I come across? A GORGEOUS blue merle Smooth Collie boy. 1 1/2 years old. I called the shelter to ask about him and make sure he was not going to be euthanized as he was a no brainer adoption to a collie person. I kept tabs on this dog until our local Collie rescue picked him up. Now, he is with them and has probably found a home with someone looking for a purebred collie to adopt.
My point is, you can't tell people where to get their new dog from, but you can ALWAYS suggest adoption from either a local shelter, or a breed specific rescue. Sometimes, once you put that into someone's mind, they think about it more and will do it. There will always be a place in this world for shelter dogs and pups from responsible breeders. The real issue is when people don't spay/neuter dogs that should not be used for breeding and when people breed poor quality dogs. If we could stop backyard breeders, puppy mills, and irresponsible pet owners, we could DRASTICALLY reduce the amount of dogs in shelters.