Movies and books

Movie versions of books (or book versions of movies, or theatre versions of comics, or whatever) shouldn't be thought of as a movie version of the book. That's just setting expectations that can never be met. They should be thought of as independent, loosely inspired works instead.

Interestingly, video/computer games based off movies are thought of in this way. So are, I think, theatre versions of whatever. It seems that it's mostly just movie versions of books that are plagued with the bizarre presumption that they're supposed to be completely faithful re-enactments of the original. I wonder why?