Although the Thoroughbred is primarily bred for racing, the breed is also used for show jumping and combined training because of its athleticism, and many retired and retrained race horses become fine family riding horses, dressage horses, and youth show horses.horoughbreds in the United States have historically been used not only for racing but also to improve other breeds. The early import Messenger was the foundation of the Standardbred, and Thoroughbred blood was also instrumental in the development of the American Quarter Horse.