Hiding information is the engine of narrative tension.  By concealing a character's true motives, backstory, or plot details, writers create gaps that invite the audience to engage.  This deliberate concealment—often referred to as the iceberg theory—transforms a passive audience into active participants.  

Drives Curiosity and Suspense: 
When key information is withheld, it forces the audience to ask why or what next. Instead of giving all the facts up front, a skilled storyteller teases clues that create narrative drive.   
The "How-dunit": Hiding the perpetrator or method builds mystery. 
The Backstory: Hiding a character’s emotional wound explains their current flawed behavior.  

Creates Dramatic Irony: 
Sometimes information is hidden from the characters but revealed to the audience. This gap allows the viewer to see the impending danger or misunderstanding, which builds agonizing, engaging suspense. 

Enables Powerful Character Arcs: 
A character's true identity is often hidden beneath a mask or a false sense of security. As the plot progresses and the "hidden" aspects of their personality or fears are forced to the surface, the character undergoes a meaningful transformation. 

Deepens Subtext: 
Beyond plot secrets, stories often hide their deeper themes or meanings. Allegories and metaphors allow authors to explore complex moral issues or human experiences in a way that feels natural, allowing the reader to discover the true message on their own. 

Allows for Rewatchability: 
When authors weave hidden clues and foreshadowing throughout their work, the story rewards audiences with a completely new experience upon a second viewing or reading.