It's an urge as old as Cain and Abel. Blood cries out for justice. People have an innate desire to know that the wrongs of the world will be sussed out and justice addressed. Murder and ID shows offer this reminder for those who need it. Horror shows are about testing your psychological mettle. Can you face up to your fears of death and retain your footing? I don't like the test or feel it's necessary, but this is why people watch it.