Why is The Namesake by Jhumpa Lihiri in the third-person narrative?

First person and third person are points of view in literature. First person (I, we,) limits itself to the point of view of a single narrator, whereas third person (he, she, they, it) is able to adopt multiple viewpoints in the telling of the story.
In the novel The Namesake, Jhumpa Lahiri tells the story of a Bengali family from Calcutta who immigrates to the United States. In an interview, Lahiri stated that she wanted to write about a boy with a peculiar name and about the importance of learning to accept what we inherit from our parents. Although the main character is the son, Gogol Ganguli, the story begins by focusing on the parents, Ashoke and Ashima Ganguli, and how they come to choose the name that they give to their son.
Because the story begins at Gogol's birth and shifts viewpoints between characters and even between generations, it is important that Lahiri uses the third-person narrative. In this way, the scenes, events, and situations of the story can be described more comprehensively when it isn't limited to a single narrator.
Additionally, readers are able to receive complex portraits and memories of several important characters: Gogol, Ashoke, and Ashima, in particular. Because the story spans many years, the author is also able to use the third-person narration to summarize gaps in time whenever necessary.

Jhumpa Lahiri uses a third-person omniscient narrator in The Namesake to provide the widest possible perspective on all the characters and events. Although Nikhil Ganguli, known as Gogol, is the protagonist, much of the book concerns the viewpoints of other characters. A first-person narrator limits the author to giving only information that is known by that character. The other members of Gogol’s family are especially important. Part of the book takes place before his birth as his parents make the transition from living in India to living in the United States. Other information about his father’s earlier life, including the train accident that set in motion bestowing the nickname of Gogol onto his son, is relevant to the story, but Gogol himself learns only what his father feels able to reveal. Using a third-person narrator enables the author to give the reader a fuller context.