Maybe in previous years the assumption of OP was right. But what I see nowadays, after online betting platforms got extremely popular, is that people gamble as a last resource to achieve wealth. They don't have a decent income, they have lots of expenses and little time, so they gamble in despair trying to overcome all those difficulties immediately.
Add this to the fact people nowadays are immediatist. They can't wait too long for something to happen. They want everything for today, and that is a consequence of accessible internet and smartphones, which bring information and pleasure in real time (which are also addictive, just like gambling).
Just to finish, add one more element: social medias bring the daily life of successful people, so the average subject keeps consuming that kind of content, wishing for himself the same he watches on the social medias. The more he consumes this content, the more he will compare it to his personal precarious life, getting more and more desperate to find a magical trick to rever this situation. Then gambling looks plausible.