Why is it that in the movie, "To Kill a Mockingbird", Mrs. Dubose's house does not burn down but in the book it does?
Further to the earlier excellent answer, I can understand the questioner's puzzlement on this particular point because Mrs Dubose actually appears early on in the film and then totally disappears. It would seem therefore that the original intention was to include the Mrs Dubose story but then, for time or other editing reasons, it was dropped. It's a case of sloppy editing in my view: episodes like Mrs Dubose, the visit to First Purchase, the Missionary Circle and so on are 'stand-alone' in the novel and could easily be used or omitted according to the film director's preferences and requirements, but in the case of the Mrs Dubose episode she is introduced and then forgotten. Just one point of correction: it is not Mrs Dubose's house that burns down but Miss Maudie's.
In all movies based on novels, the director usually must make changes because novels can contain many more details than films. The director has about two hours to unfold the story. We know that it can take far longer than that to read a novel and understand all the nuances of the author. In this case, the director was more concerned about telling the story of Atticus, Scout and Tom Robinson, than he was about the rest of the characters in Maycomb. If you watch the film closely, you'll see that other scenes and characters were also left out of the film. That's why one cannot substitute seeing the film for reading the novel. No matter how good the film version is, it cannot contain the rich details and characters of a well-written novel.