>>Why don't ghosts come from the future?In popular culture, ghosts are often represented as a snapshot of a moment in time, endlessly repeated. Mostly these snapshots relate to incidents from the past - eg. a headless horseman, Mary Queen of Scots and the like.Setting aside disbelief/ scientific scepticism about ghosts generally, is there any theory that would explain why ghosts could not equally appear from the future?<<

Setting aside disbelief/ scientific scepticism there is no reason why pigs shouldn't fly or rivers flow uphill or blood come from stones.

For those who believe in ghosts from the past, it is only a small leap to believe in ghosts from the future.

Why don't ghosts come from the future? Because the future has not happened yet. It is not fixed as any minor decision I make today will change my future (and possibly yours). If Ghosts come from the future then the event(s) that caused the ghost in the first place will have had to have already taken place, thereby deteremining that particular future and rendering todays decisions pointless and ineffectual.