They’re less likely to have genetic health problems
Dogs from breeders often suffer from health problems as a result of poor breeding practices. Additionally, purebred dogs, in general, are more likely to have genetic issues due to being bred for specific purposes over generations.
The possibility of illness only increases if the dog came from a puppy mill. But the poor conditions and lack of veterinary care at the facilities can increase the chances of health complications. Adopted dogs, however, are given veterinary care in the shelter before they are adopted. Additionally, many are mixed-breed dogs, lessening their chances of genetics causing problems.