Many of the English language's greatest literary works, fiction, nonfiction, and poetry were first published privately or semiprivately, as each author, many later to become famous and even iconic, sought to start their careers. Often a first work turned out to be an author's best work but attracted no publisher to a then unknown literary artist at the time of first completion.
By semiprivately" we simply mean the author was published, probably in a small print run, by a small publishing house or bookshop/publisher who was a personal friend or acquaintance. If memory serves correctly Hemingway's in our time (as opposed to the later In Our Time) and (T.E. Lawrence) Lawrence of Arabia's Seven Pillars of Wisdom, were similarly first published.
For myself, as a painter, I only resisted writing early on because private publishing was too expensive for me and seeking a large publisher didn't interest me due to my artist's personality. As a capable sketch artist and painter from an early age (arguably even a bit of a child prodigy), I would never let anyone take a wet brush or pencil to my work. Neither would I with sculpture or any other artistic medium. What artist would?
So why let my writing be edited? It is the same thing. The answer is that publishing houses invest money to mass produce a writer's book. To do so they must save cost and make a book more readable to more people, to larger interest groups interested in that type of book, larger "mini-masses," if you will.
Thus some, perhaps most, modern era literary artists (writers) saw their work cut up. Again if memory serves, Look Homeward Angel, a seminal signature work was drastically cut, and the artist, Thomas Wolfe first thanked his editor and then, matured years later, lamented the edit. Both the edited and uncut versions are available now.
As an artist, with a wide and varied background, I trust my "product," flaws and all, and have been more that encouraged by the praise of very experienced, educated, knowledgeable readers who are widely read in many genre and have contacted me. In my humble opinion, we previously had editors, not because they were naturally necessary, but because of the expense of printing. Now printing is within the writer's, the "literary artist's" reach. Publishing is part of the writing process now. I find the idiosyncrasies of a writer to be part of their work. Some break rules intentionally and set knew standards. If done well, that becomes part of their signature style. Are editors necessary? Yes, often. There are those writers however who have unique styles, my almost painterly use of spacing and punctuation, for example. An editor might have wiped all that out.