Being greedy is nature to those who experience a great loss or maybe being victimize by scam, unstable price, etc. Some other people are not really greedy as we all.think of them but they do such strategy of holding in preparation of the changes of the price so that they can make sell and gain of price rise.
It doesn't depend on what happened to the person. Just the nature of man being insatiable as he did not give him all the little and little.