Uncontentment is human nature and that usually happens in gambling. Most players bet and can't control themselves from betting because of the aim of winning or as they chase the jackpot. Those who put their false hopes into gambling usually focus on their goal and not on their current betting status which usually result in consistent losses.
True that, greed is triggered by uncontentment on the gambling result even though the gambler has amassed ah huge amount of money. They keep on betting until they lose their winnings. Just for example a person who is playing slots online will keep on playing even though he had a maximum multiplier win on one of the slots because they are not contented on the amount that they won and wanted to get more winnings.