Why do YOU think the author had the setting limited to one particular city in divergent?

The author likely chose to limit the setting to one particular city in "Divergent" to create a focused and immersive world that highlights the societal divisions and complexities within that environment. By centering the narrative in a single location, it allows for a deeper exploration of the factions and their ideologies, enhancing the themes of identity and choice. This confinement also heightens the tension and urgency of the characters' struggles, illustrating the consequences of their decisions in a tightly controlled society. Overall, it serves to intensify the story's conflicts and character development.