Its just another case of where there is a market there is a profit. Thats what makes the screw turn and keeps the wheel spinning. You ask why do horror films appeal to anyone, those people would ask, for example, how does country music appeal to people.... Ifs a persons own choice and interest. I like classic cars but the kids across the street like ricer cars. Its just what they like but a ricer car has absoluty no appeal to me.
A friend who is deeply into the horror genre explained his appeal to the films as this: "a magician can only do so many tricks before he has to come up with something no person has ever done before, now apply that to a horror film". In other words, new ways to kill, mame, torture and terrorize but in the name of fun, entertainment and creativity where nobody is actualy hurt. To me personaly that sounds like a combination of pop 40, rap and country music all in one tight package. The horror, the horror....