Fans already know to expect changes to be made when adapting a book to the big screen, particularly with a trilogy such as The Hunger Games. This is the case in most book-to-movie adaptations, like the film adaptations of book series like Harry Potter, Twilight, and Divergent. It could be for simple reasons such as time constraints or a limited budget or technology. It could also be for the sake of visual and narrative cohesion. For these reasons, it was no surprise that changes were made to the story of The Hunger Games when the novels were made into movies.
Source：https://www.cbr.com/hunger-games-differences-between-books-and-movies/
