An author would write in a first-person perspective to show the internal thoughts and conflicts of a character or person. By using these personal pronouns, an author allows readers to view the story or writing from the point of view of one singular person. This means the reader is understanding events, emotions, etc. from the eyes of one person. That can limit their knowledge in the story, as they are also taking in information from one source, as opposed to multiple or from an omniscient narrator.