how does the writer's choice serve the best?

Question

Why is it that the writer gives only one character omniscience and doesn't permit the other character a voice?

Answer 1

I'm assuming you mean stories written in the first person, since third person allows you to know what every character thinks or feels. In first person stories, changing the voice confuses the reader. It's hard enough to write what one person sees or feels, so the secondary get short shift. Unless you then write a story from their viewpoint and have another book.