Cos he was born in the 22nd century, around 200 years after JFK was assassinated. Even Abraham Lincoln isn't 200 years ago for us and we think that was a long time ago. It would be the same as you knowing about the first few presidents. Now you probably do, but that's purely because they were the first ones but unfortunately that's what 200 years ago from now is. If they were just randomly placed in the middle of tons of presidents you wouldn't. There are probably also around another 15 presidents ontop of all we've had so far from now to 2150 that Lister would be aware of. So, out of all of them, remembering one president who died 200 years before he was born, why would he know? Now sure, not many have been assassinated so far, but that's just until now, there could be tons more that Lister would know of and remembering just 1 of them is a bit of an ask especially for him.
@OverWims I know all about British kings, and I'm in America over a thousand years after it started having proper kings lol. Alfred the Great is I think is the first, at least of England.
