I'm at first inclined to think that a lot of the Chosen Nobility Hero stuff comes from fairy tales, though when I think harder about half of the fairy tales feature a working-class protag who's often special by nature of being somewhat mentally deficient or something.

Of course, there's also the point that nobility can afford Hero Swag and also snazzy clothing. :V

As for the diplomacy thing, I expect that something involving compromise and all is just a lot harder to write, both because it's more complicated and also because there's not as much of a narrative tradition for it, so one really HAS to do a lot of work, as opposed to the easy path of "Follow Your Heart" Archetype.