Obviously you don't know much about dogs. The American Pit Bull Terrier was cultivated through selected breeding of fighting dogs. Other breeds such as Bulldogs and Bull terriers were bred for the sport of Bull baiting, which you can google if you've never heard of it.
Not all dog breeds were bred for hunting. Some were bred to be guardians of livestock or people such as the Caucasian Ovcharka, Doberman Pinscher, and Rottweiler. Although the rottweiler was also bred to work pulling carts. Other breeds were bred for herding like Austrialian Shepherds, German Shepherds, and Collies. Yes some were bred for hunting but I would hardly say that most of the breeds out there were bred for hunting.