What do you think happens when you die?
I think of bad things. I think that you have to restart your entire life, with no memory of the previous life. If that was true, ghosts are people whose poor souls can't restart any more. They can't take any more of that. Once people remember their before life, they turn into ghosts. If they say anything about it, they scream at the top of their lungs and disappear.
Sorry if I made you feel sad.