Why doesn't Ernest Hemingway use correct grammar and punctuation?

Why doesn’t Ernest Hemingway use correct grammar and punctuation? I am reading A Farewell To Arms, and it seems that he refuses to use commas, or periods and frequently has run-on sentences. Aside from the fact he was a part of the greatest generation and drunk, why does he do this. I mean, all things considered, he has great content, buy his presentation feels sloppy.