For those that gamble for fun, I don't think they need another reason for them to gamble rather than just playing and having that fun they came there to do, where losing the game is just part of the game for them and they accept it in good faith.
But for anyone who gambles for fun and wins, they probably like to continue in order to chase their losses. By doing this, they believe they will one day be able to win a game that will help them recover all that they have spent during the losing season.
Those are just what I can think, and I also believe that we all have individual beliefs as to why we still continue gambling even knowing the fact that we have lost enough and always don't have winning luck. We all have that individual inner spirit that will either push us to try hard or will advise us to stop.
One thing I learnt about gambling is that it's very good to stop gambling when you're losing quit gambling for two or three days before you can go back again because if you try to gamble more, you're very likely to lose your money.