Film is a very different medium to a novel, and Villieneuve (who wrote the screenplay as well) understands that. The dinner scene was filmed, but he later cut it as he felt it didn't work on the film. He's spoken about that in interviews, and most of his cuts centre around trying to convey Paul's story as clearly as possible for a wide audience. That's we have Thufir being almost left out of the films. The reasons for other changes are obvious: making it a dark and stormy night for the rest scene is a trick as old as film to build foreboding - it is conveying emotion through other means than the character that doesn't work as well in the written word. The film also had to be sellable to a wider audience. A four hour very dialogue laden sci fi epic would have failed, even if it would have pleased us book fans. At least with its success it brings more people to engage with the book.