I think the reason why they are getting addicted to gambling is just because they want an instant money, they want an easy profit which is not possible. Beside, I think another reason is once they play gambling and lose they tend to play again to retrieve their loss then it'll become habit of them which can conclude that you became an addict.
Well, who doesn't want easy money

. If they will give you way to have easy money, will you refuse it?
These is the main problem why gamblers are getting addicted into gambling. They see gambling as a quick rich scheme which is wrong. Maybe a quick rich if you are very lucky enough to win consecutive times. Gamblers are getting addicted too because they are losing their money and they want to retrieve it. They can't afford what they lost.
But most of the time gamblers only lose money so I don't think it is easy money at all. You bet, you lose, you play again to get back what you loss, yet you still loss, then play again and etc. I mean, playing and playing all over again hoping to retrieve the loss money is wasting money at all. Gamblers get addicted because of greed, playing may be fun and exciting but when you start losing money, it ain't no fun at all. Don't get addicted, control yourself and most importantly, don't ever think that gambling is a good source of money. It is a game that is so risky.