I've just come home from Epsom racecourse, after an evening race meeting. Horse racing is known in Britain as 'the sport of kings', presumably because it has always been popular with royalty and the aristocracy. Certainly, the present Queen is a fan.
Sport of kings is in the OED, but the racing meaning is a 20th century meaning, and there were two other senses before 'racing'. The original 'sport of kings' was war (17th century), and after that it was hunting. Horse racing came to be considered the sport of kings in the 20th century.