WayneLigon
Adventurer
That would be a good thesis topic. I think a lot of factors contribute to it, but I would guess their closeness to Dogs (Our Best Friend), the associations with the American West, and the idea that they are so much like us - they are a social animal, and a social hunter, but don't have a quasi-disturbing resemblance to us like chimps do. Take all those things, mix in the romantic notions that movies and TV have planted in our heads, and there you go.