By using a so-called "minor character as narrator" point of view, the author is able to inject his own commentary on the characters and events in the story without interfering with the dramatic movement. In other words, the author does not become an "intrusive author." Nick Carraway has plenty to say about everything and everybody in the novel. He is a judgmental type of person, although he claims to be very broadminded. Fitzgerald's only other alternative would have been to use the "omniscient third person" point of view, because he could hardly tell the story from Gatsby's, or Daisy's, or Tom Buchanan's point of view. If the author had tried writing his story as the invisible omniscient narrator, he would either have had to leave out a lot of the commentary on his own story, or else he would have had to be an old-fashioned intrusive author. That might have made the novel longer and more episodic and slower-paced. Fitzgerald was a young genius and might have written a brilliant novel in that alternative manner, but Nick Carraway as the minor character narrator seems like the right choice.