See, everyone is always asking me why I get so furious when Hollywood makes a bad film adaptation of a good video game, classic comic book or great piece of literature. It's because people have a tendency to associate the low quality of film adaptations with a perceived low quality of the original source material.
This is why people don't read anymore; bad film adaptations. Some fool makes a lousy adaptation of Halo, The Punisher, or Dune, and people critically question (or outright dismiss) the worth of the original video game, comic book or novel. A bad movie becomes the de facto public face for the source material, because movies are the most pervasive medium in popular culture. Make enough bad movies from a common medium and you can diminish the perceived worth of those entire mediums.
This is something the idiots at the HLP don't understand. Every lame KJA novel, every Peter Berg adaptation, every lame product they produce under the "Dune" name ultimately undermines the original. Yes, sales of the original increase somewhat via exposure, but it's ultimately a short-term, cannibalizing effect upon the original's reputation. In the eyes of the vast majority of people who do not know better (or care to know any better) the original becomes synonymous with a perception of poor quality. People generally don't have time or patience to swim through a sea of shit to find the few gems. People are already filtering popular culture every day. Thus, most people won't bother to research and learn what Dune to avoid to find the "good Dune". Produce enough bad product under the "Dune" label and most people simply dismiss ALL DUNE by default.
Besides, most of these increased sales of the original are not by readers genuinely interested in Dune; they are sales by people reading KJA books and hence they are disappointed when the Frank Herbert books are "not like" what they read before.
To use an analogy, imagine you're enjoying some mindless, fast moving action flick only for the film's second half to turn into a slow moving, introspective and existential drama. Even if you happen to like both genres, you're totally perplexed by the sudden shift in story and angered because the movie isn't fulfilling as an action film and is only half a good drama. To digress back to Dune, fans might even dismiss Dune because they were in the mood for simple, undemanding fiction like KJA's books. Thus they miss out on Dune, which is ultimately much higher quality and more rewarding work of literature.