You can't be as old as I am without waking up with a surprised look on your face every morning: 'Holy Christ, whaddya know - I'm still around!' It's absolutely amazing that I survived all the booze and smoking and the cars and the career. ↗
Number one is that it just scares people! Your hair is standing up on your arms, or at least that there's a few moments when you're jumping. That's what makes it a good horror movie. ↗