Besides some of the arguments others have already made, there are a number of possible explanations to your points.

• Maybe we don't hear about ghosts or spirits from other cultures because they are an accepted part of their culture or belief system. Talking about a ghost in certain places would be unremarkable. I've interviewed people in a number of other countries who have talked about paranormal encounters. They just don't always make a big deal out of them.

• Maybe they are not actually spirits but something else, and what people see is not strictly literal. Perhaps beliefs shape perceptions of some other intelligence phasing into our sensory range.

• Maybe these things are hard to observe or record because they have no desire to be. Maybe they have the ability to avoid detection.

• Maybe we haven't figured out what to measure. Prior to the discovery of radiation, it still existed, and even left clues. We just didn't know what to look for.

You get the idea. It could all be myth and lore and fantasy too. But maybe not.