I think its more on the money side that triggers the gambler to be addict on that, though its a nature in every human to be addict on something. Its just like people who are addict on Dota, ML, other online games or in any KPOP group, the only difference is the money involve. Winning creates more excitement and that is why gambler continue to play after winning good money.

This can be a good reason, because controlling yourself to stop playing is very hard and if you have weak emotion you will lose money and that makes a lot of gambler broke for a moment.