When we play gambling, than it is normal that we become greedy. Because everyone play gambling to earn money and in this way, if we become greedy than sometime we win in behalf of our greediness.
That's why when you go for gambling shouldn't load a lot of money instead just load how much you can afford to lose for that session and gamble. If you do like this then no need to worry about how much you lost but you can enjoy the games. I never load more money to gambling site and always play with small amount to enjoy my time.
Is that the bottom line reason why gamblers became greedy in a long run? Perhaps, not all players/gamblers become greed once they start to play in gambling. Because I still do believed that there are some gambler played gambled just for fun and entertainment or sometimes for relaxation only. But in reality situation, controlling our emotions could be one the tools to prevent greed on gambling.
yes not all people will become greedy once they start to play gambling. But those who wants to play gambling to make money that people will become greedy when they lose money in gambling. And most of the newbies will not play gambling to have just fun and entertainment. They look some easy money in gambling, but it is not easy in gambling. So in this process, they will lose control on games and become greedy. Self-control is the only solution to control greediness.