Why do ghosts have to wear sheets over their heads.

[Rev. Rye]

There's a reason that ghosts are seen in sheets, and my main source for this is a TVTropes article: it has long been a tradition in fiction to portray ghosts as, if not dressed as they were in life, then they are usually dressed they were in death. For a long time, this meant grave clothes and a long, white, flowing burial shroud. And sometimes, especially in old productions of Hamlet, they were portrayed as suits of armour. Eventually, it became too unwieldy, expensive, and ridiculous-looking to use, and so, it became common to see ghosts buried in their shrouds. And somehow, the fact that we no longer use burial shrouds like this has no bearing on this tradition.