i don't watch horror movies. and only rarely will people ask why. the primary reason being that i just don't find that sort of story line very interesting. the very close secondary reason is that you cannot unsee things.
perhaps an example is in order. you know when you will be driving around or out with friends or in a store and you'll hear a song. or you'll smell someone's fragrance as they walk by. or a friend will phrase something just so. and for a moment, or more, your heart will drop in your chest and you'll disappear for a second or two. all because it reminded you of a place and a time.
i fill my head with all sorts of things and as inane or unfortunate as some might be, i'd rather flash to that on occasion than some made up entertainment gore.