Before Michael Myers had a dumb origin story (the druid thing, not the mom being a stripper thing) and was apparently immortal, he was simply The Shape. In fact, in the original Halloween, Laurie Strode isn’t Michael’s sister. It’s never brought up until the sequel (which wasn’t even on the table until the first one did so well). Now think about what that means for Michael’s intentions. He’s stalking this girl, killing her friends, and chasing her all around her neighborhood… for no reason. He’s just gorilla-shit crazy and she happens to be the first person he lays eyes on. Consider how all the urban legends of the 70s, 80s, and 90s (before Snopes was around to debunk them) primarily centered on deranged drug addicts and other criminals committing pointless crimes, just for the thrill or because Satan told them to or something. This film is the natural extension of that cultural fear.
Another aspect of the film that I think gets frequently overlooked is that this is Laurie’s neighborhood. Her own hometown. And she’s not safe there, even with people who know her only a short distance away. The 70s were the point at which safety at home became a huge social issue– a trend that continues on into today. Again, the film really captures what freaked us out during that time period (and on into today… Minus, you know, terrorism and stuff).