It allows people to use their imagination more
Some people might be better able to use their imagination when they read a book than when they watch a movie. Those people might prefer to creatively think about a story instead of being forced to see it in a certain way
Some people can get more emotional with books
Some people can get more emotionally affected by books as they describe things in detail. Those people might fail to get the same emotional arousal from the movie.
It makes the characters more relatable
As a person spends hours reading a book he becomes more connected to the characters and can easily identify with them. Because movies are short it might be harder for some people to relate with the characters.
Books are more detailed
Some people prefer to read a book than watch a movie because they are interested in the small details a book can offer.
Movies are too stimulating for them
Some people find movies so stimulating and prefer a calmer way such as reading to know the same events.
Plots usually get changed in movies
When a movie about a book is released the plot can be changed and many scenes get removed. Some people believe this makes the movie less rich than the original book.
The prefer to interpret events in their own way
Because movies usually show things from a certain angle some people prefer books over them as they prefer to interpret the events in their own way. (See How to read a book really fast?)
Getting more understanding of the characters
Books usually describe the thoughts of the characters in details. Some people prefer books over movies because they allow them to understand the characters more deeply.
Production budget can fail to show what’s in the book
Because books rely on the writer’s imagination while movies depend on a budget movies can sometimes fall short and fail to express what’s in the book properly.
They want a longer story
If a person likes a story so much he might want it to take a longer time. Those people might prefer books over movies.
They generally like reading
Some people find reading to be an unpleasant activity. The people who prefer books over movies are usually among the ones who already like to read. (See How to Read 52 Books a Year?)
Why some people prefer Books over Movies?
Why do some people prefer reading a book than watching a movie? Books vs. Movies: Why Many Prefer Books Over Movies