Part of it is – I think – the result of early training for all of us. We are taught that writing is an art form, and therefore can’t be tamed or it somehow fails to be authentic.
Is this true? I don’t know. As I write this, I can hear my journalist friends laugh at me, which is funny since the nearest one is several hundred miles away.
On the other hand, writing as a journalist and writing as a fiction writer are different. Even writing a fictionalized version of reality is different. I could write Plain Jane, my fictionalized biography of Jane Seymour, in three days because the central facts and dates could not be disputed. Jane could not, in fact, in the middle of the book, decide to run away to sea and become a pirate (something Kathryn Howard, in No Will But His very much tried to convince me was an acceptable ending for her story.) I couldn’t suddenly realize how much the story would be improved if I gave some horses the ability to fly, and then go back and retcon the work so it could have flying horses.
Practically any fiction work, not based on hard and fast facts calls for more invention than that. Even mystery where you can halfway through the book go “What if the dagger belonged to the king? It would be a lovely red herring.” Even romance where you can go “Wait, what if I give the main character a tragic past involving dolphins?”
So having your full faculties about you and being fully in the head space of the work is more necessary to a novelist than to a non-fiction writer. I can, more or less on command, given some time, write a summary of facts, or even an opinion piece. But when I’m frazzled, ill or distraught, I can have the hardest time seeing the “full world” of a novel and the things that can affect my character which are not in the outline.
I know it’s fashionable to say that the quality of books in general went down when publishers put authors on what I’ll call “the treadmill system.” I’m not sure this is true. A lot of the golden age authors (whatever the golden age is considered to be for science fiction, mystery, etc., were on what I’d call a “write by the yard system.”
“We need 36 inches of story by tomorrow, can you deliver?” seems to have shaped a lot of the pulp era writing, and for all that, it is still considered a golden era. To go further back, Dumas, Dickens and a half dozen others turned out copy with such fluency that people suspected them of having helpers chained in the basement, writing things for them.
However, I will admit that reading some of the books from the more rushed part of author’s careers – i.e. when they were turning out the most books per x amount of time – you often get a certain feeling of “thinness.” In textile terms, the fabric is beautiful, the pattern intricate, but you can see through it. You get a feeling the story is sort of a hastily erected Hollywood scenario, with nothing at all going on in the parts where the light doesn’t shine.