There isn't much anime horror. im guessing its not as popular. Im also guessing that anime companies like to use the same formula as other animes. If you make something completely different it might not make money, and the company loses money. That's why you see so many slice of life, romance, harem, giant robot, shonen, and sports every month.
Would be cool if they made a anime like Air Gear, but use skate boards instead of roller blades. Then again the show failed and didn't make that much money, so it might never happen. Unique animes hardly happen, like I said it could mostly cause people are scared of losing money, or not making as much as other popular animes. Though they do happen once in a while like, Trigun, cowboy bebop, samurai champloo, hellsing, FLCL, serial experiments lain, paranoia agent, and jojo's bizarre adventure, but those kind of animes hardly ever happen.
The creator reads American comic books, and you can tell, a lot of the characters in the show have the same powers as a lot of the X-Men characters. Even has the same story as the X-Men, kids with powers learning to control their powers and train at a school.