For me it's fan service, but there must be more to it that I'm missing. Apparently it made nearly half a billion dollars over a budget of 165 million, so it cannot be just hardcore sci-fi fans. Chances are it's simply not my cup of tea, or not the cup of tea of a few people who value other kinds of experience on movies. I have a cousin who loves the movie and he says that the cinema experience is amazing, the images and sounds and the whole thing kinda pulls you in. Maybe that's just it: technical quality.