I think that you've described it perfectly - to get that momentary hit of dopamine.
It's obvious that people do it for financial reasons as well, but at the end of the day, that is not what most people look for (unless you're one of the people who see gambling as a means to recover losses from elsewhere, like trading). Especially lurkers on dice sites, they're obviously not influenced much by finances.
Honestly, in the more extreme cases, it is a pure, unadulterated addiction to chemicals produced in your brain - that is all.
I think they need a way to release their addiction (if they have) and come to the professional that can help them to cure that addiction. We don't need to think that gambling is a way to recover losses from elsewhere. What we need is to enjoy the game, spend some money, quit gambling. If we can do that, we never have a problem with gambling, and even we will enjoy the game, and maybe we can also release the stress by playing gambling in the limit time.