...I'm a bit confused about the timeline. The ex-Mayor said that she was the only one alive who knew the rules of golf. But the main guy was only a kid when the aliens first came and there are people older than him, so it's hard to believe human knowledge of the old life got lost so quickly. Unless I'm reading too much into it and she was just making a joke about her age
Not everyone knows how to play golf, and I get the impression that a majority of the Earth's population was killed during the Pale Wars and Arkfall. It's possible that most of the golfers in the world didn't survive. Wars and disasters on that scale have a way of destroying culture and history as well as lives.