All gamblers I ever met do it for fun, usually with money they can afford to lose. Look at all the people that “play their numbers” every day at 7/11 or the gas station or super market. Some habitual gamblers are not actually addicted to gambling. They are addicted to losing, and have a subconscious secrete desire to lose.
Starts before they are three years old. Notice, when they are lucky and win, they keep on playing until they “succeed” and lose. And its not only gambling. They tend to put themselves in other positions to lose, like arguing with a cop, or asking for a date with a girl that far outclasses them and get the NO answer.