The western Ideology

"The hero never really wants to accept civilization as embodied by the woman (who brings with her from the east the notion of community, family  and so on.) Rather he is always desiring to be on the move in the wild west. The cowboy with his restless energy and rugged dogged individualism, is the western embodiment of american frontiersmanship, or at least the myth of that frontiersmanship".

"The fact that the cowboy or gunman is always represented as being caught between that two values points to the ideological contradictions inherent in the myth of that frontiersmanship. The hero's actual ambivalence reveals the nation'sown ambiguous attitude towards the west. Civilizing the west meant giving up the freedom it represented, including of course the freedom of the individual, a high price for Americans to pay for national unity"

Typically, this is why the hero never settles with 'the girl' at the end of the film.
The west had not yet been won, and the image of the gunslinger riding off into the haze of the desert represents these "inherent contradictions".
The myth of the cowboy can also be read in Freudian terms.
In terms of spectatorship then, one might look at ncfom and consider how it subverts our expectations of the western genre.
Additionally, we might also consider the expectations of the western genre.
Additionally, we might also consider the expectations of spectators when watching a Coen brothers' film.