Why do some people like horror films?
Horror films can provide a safe way for us to mentally rehearse how we'd handle real danger.  Some people actually enjoy the scary emotions that horror films elicit.   It can provide a unique adrenaline rush, somewhat similar to other fearful activities, like white water rafting, jumping out of airplanes, amusement park rides and flying in a small aircraft.  For many, horror films are their least liked movie genre for those same reasons.  They might prefer a romantic comedy or action triller, without all the blood and diabolical antagonists.