I think it's just cheap. And what about if it's athe estate and not the author? Maybe your point still stands. I think I see it more cynically, just cheap and perceived as an association with a more popular medium, with little regard to the actual text. (Obviously the film/screenplay may also have little regard to the actual text, a lot of film adaptations are poor and also probably quite cynically done too). It's an easy win in the reverse, the fans of a book are an almost guaranteed audience for a film adaptation. I don't think always/necessarily it is done with good intentions.