To be exact, people are in gambling for the reason that they would like to win and have some money.
That's the main reason for majority of people but not for everyone though, because there are people who do have a lot of money to burn in gambling and they just find gambling the best way to enjoy their life even if they have to lose but they will never lose more than they can burn.
That was crazy actually if we've been addicted to gambling just for stress reliever, having fun or social engagement. What makes us relieve from the stress in gambling, if we are able to hit the jackpot prize.
Believe it or not there are people who consider gambling as a stress reliever, it may sound weird but those rich people have the capacity to gamble and lose money just to socialize with friends.