In real life, people do irrational things all the time. These things serve no purpose for anyone, at least no conscious purpose. They are thus truly irrational, and often highly destructive.
In a movie, if someone behaves irrationally, it seems to serve the story in a contrived way — like the writer/director has made this person do something they have no reason for doing in order to serve some preordained narrative end. And the audience won’t buy this — people in movies have to seem like they’re acting of their own free will, rather than fitting into a larger narrative scheme, even though, of course, that scheme (the movie’s plot) has no way of manifesting except through them.
So, I think, people in movies are not allowed to behave as irrationally as they do in real life because true irrationality is not achievable in a work of art that has an author.
The work of any artist that rises to being an -esque has some element of humor in it.
Somewhere, in great art (at least great narrative art), the lines of horror and humor cross … no great art is dead-serious all the time (except maybe Cormac McCarthy’s). Art that achieves the state of -esque (Pynchon-esque, Pinter-esque, Kafka-eque … Lynchian, Cronenbergian, and Beckettian as honorary -esques) describes the world as only it can, granting those who come in contact with it a portal into a place they recognize as real but could not have accessed on their own.
Work on this level is morally neutral: it’s describing reality as the artist encounters it, as if he or she were a highly articulate alien visiting earth, not arguing for how it should or shouldn’t be. This encounter, for its disarming combination of surprise and recognition, is funny.
Art that becomes an -Ism, on the other hand — like David Foster Wallace’s in its later years, or George Saunders’ some of the time — contains a plea for change, an ideological, almost Evangelical dimension demanding that readers become better, strive for more, lift themselves up … which, for me, much as I appreciate the sincerity of the sentiment, keeps it short of greatness because it refuses to take on the world as it actually is. To insist instead on a better world feels like a failure of attention on the artist’s part.
And this isn’t funny — it’s grim, no matter how much humor it strives for.