Back in the '80's, on the old "Happy Days" TV show, someone once asked Fonzie why he never went out on Saturday nights. He replied, "I never go out on amateur night." That's pretty much how Buffyverse vampires must look at Halloween, as a bunch of wannabes and fantasizers out pretending to be the real thing. Almost certainly, the real things couldn't watch the antics of the happy meals on legs without laughing out loud, which would have made stalking almost impossible. But that's the only night of the year that all the self respecting creatures of the night take off. It's open season for the other 364 days of the year.