People often ask "why should I spend the money to buy a purebred when there are lots of puppies out there that are mixed breed and would make a good pet?"
Genetics and breeding play an important part in what you get as an adult dog. So put simply, if you have two dogs that have good temperaments, the odds are 98% your going to get a litter of puppies with a good temperament. Selecting for a Service/Therapy/ESA dog requires even a higher level of great temperament, intelligence, and ability to connect to humans. This is why I am able to produce great service dogs.
Below is an article that Meryl Cohen (dog trainer and Cane Corso owner) wrote addressing this subject.