I disagree. There are sub-genres and different types of horror. I love the film The Shining, but I've failed to sit through 1 Troma movie. A film like Silence of the Lambs, The Shining, or even Mr. Brooks (example given by OP) would not benefit from a porn star. Although a gory slasher film, exploitation film, or something similar to those to types of horror would most likely.
While all of the movies listed above are directed at adults, that does not mean that they will appeal to the same adults.