Times2, good breeders don't add dogs to the population of orphaned dogs. They take the dogs back if the people who bought it don't want it anymore, so that the dogs almost never end up in shelters or rescues. They do it because they love their breed, and good breeders won't have much more than 2-3 litters a year either. It's bad breeders that just breed their dogs to make money from the puppies, and don't care for health or temparement... mutts or not.
As to why it's not going to be a breed, it's easy. You can't just breed two dogs from a different breed and call that a breed. There is just no standard. Puggles will sometimes look like a pug, sometimes like a beagle, sometimes like a mix of both, basically you won't find two puggles that look alike. Could people make it a breed? Yes they could, if they really worked on it, but as the people who are breeding those designer breeds only do it for money, it's not going to happen. The only real attempt at a breed is the labradoodle in Australia, and they really don't look like the labradoodles we can find here.
As to why it's not going to be a breed, it's easy. You can't just breed two dogs from a different breed and call that a breed. There is just no standard. Puggles will sometimes look like a pug, sometimes like a beagle, sometimes like a mix of both, basically you won't find two puggles that look alike. Could people make it a breed? Yes they could, if they really worked on it, but as the people who are breeding those designer breeds only do it for money, it's not going to happen. The only real attempt at a breed is the labradoodle in Australia, and they really don't look like the labradoodles we can find here.