And writers don't edit their stream of consciousness writing, right?
You could say that old Jack never edited his stuff which made it what it is (yeah, which is bad!)
I don't think you can compare it to jazz. Even a very good writer would not write very well in one or two uninterrupted sessions. That's journalism!
Just my opinion, but I think "On the Road" has prominence only because it can neatly be identified with a movement, and that it represents the zeitgeist of a few people at a certain period of time. But that doesn't mean it's necessarily good art.
Griffith's "Birth of a Nation" depicted a movement and represented the zeitgeist of a group of white folks at a certain period of time. Well you can call that movie good art if you like. I haven't seen it, but I doubt that I would label it as such. But--hey!--it fits nicely into categorization and periods, such as scholar squirrels (Vidal's term-not mine) and academicians love!