I went to a meeting in Casper, Wyoming, in October where there was a panel discussion about the myth of the cowboy. Speaking were John Nesbitt, a historian, professor of Western culture, and author; the poet laureate of Wyoming; a black rodeo bullrider and author; Linda Hasselstrom, a historian and author; and Annie Proulx, author of Brokeback Mountain. None of them had the definitive answer to your question, but Annie Proulx said, "If I had wanted them to be cowboys, I wouldn't have put them to work herding sheep!" According to Nesbitt, what sets ranch hands off from cowboys is horsemanship. In addition, several people from the audience spoke up and there were several women who were daughters or wives of ranch hands or ranch owners who were very discouraged because none of the mystique of the cowboy rubbed off on their men, translating to viable careers for them. Perhaps the most definitive answer was given by Proulx at the end of the talk when she left the audience with a riddle: "A yellow snake, a green kangaroo, and a pink elephant walked into a bar. The bartender said, 'You're too early, boys, he ain't here yet.'"