After losing a big chunk of money, that's when you start to do bets that you can't even afford to lose or even go all in. You want to recover your loss in a single bet. You'll love the thrill. Then if you lose that round, you'll end up having more losses to recover. You'll try to recover your losses but you'll end up having more losses. Until you realize nothing's left in your bank account so you start to sell your stuffs. If this happens to you, then you are now addicted to gambling.
Let's suppose that you suddenly received a million dollars and you're a gambler. Let's suppose that your goal was to reach a million dollars through gambling. Okay, you're there. But why does it feel unfulfilling? You want more. Greed drives you senselessly, or so you think. The real allure to gambling is the thrill. Without any loss, there is no more intensity.
Essentially, you're addicted to... losing.
But let me continue.
Many would deny the fact that they are addicted to gambling even though they truly are. Why? Denial allows for more excuses to gamble in the first place.
"I'm gambling for fun".
"It's not about the money."
Despite it all, both of those phrases ARE true. The dopamine levels in your system increase, of course, when you are gambling purely for the thrill. Normally, people initially enter the hobby of gambling for the money, but slowly, they start coming back not for money but for the enjoyment of the game itself.
Rationalize.
Also, several experiments were done in relation to gambling.
Check out this: https://en.wikipedia.org/wiki/Iowa_gambling_task
Excellent citation....
Yes, there are many psychological and physiological stimuli associated with risk vs reward event responses. It is beneficial to understand those effects to be successful poker player. I giggled at your above allusion to those who are addicted to losing....it is so true and a "leak" in the games of many; knowledgeable players have an easy time exploiting that behavior.