It can help to add context for the work. For example, if the writer was from Victorian England, their etiquette might be very different to what the reader knows. So a scene in which a characters is being very rude might not come off as important to a reader unless they knew it was rude in the author's perspective when writing possibly. It also adds context to what the writer may write about and how they write it. For example if the author's background was heavily conservative, that might explain why certain characters are portrayed certain ways, like homosexuals being the villains often rather than a hero or friend of the hero or something.
