I'm not sure that's entirely true. I know and have witnessed plenty of contemporary audiences having similar pale-faced and terrified reactions. I saw the film twice on a rerelease a couple of years ago, and several of the (mostly) young people in attendance, presumably aware of the films reputation and wanting to see it out of curiosity, were visibly shaken. I overheard many terrified remarks on the way out, and also witnessed half a dozen walk-outs at the more stomach turning moments.