Instead of losing most of their income to gambling, they should use their income to meet their daily needs and save for their future needs. That would be better because they would not lose their money because of gambling and could prepare for their future too. If they have good self-control, they can use a small portion of their income to gamble but must still use clear limits so they don't gamble excessively. Having a steady income helps them survive and meet their living needs and not spend it on gambling because no matter how much money they use, it will run out, especially if they don't have good self-control.
If we can use a small portion of our income, that is enough to gamble, especially if we gamble just for fun, meaning we don't try to chase wins. We just try to enjoy our free time by gambling and will leave it before the free time runs out. By always controlling ourselves while gambling, we know that gambling is entertainment and there is no need to gamble as often as possible because it can cause other problems.
You can do them all, there is really no mutually exclusive situation between the two. You can pay for your daily needs, you can save for the future AND you can still end up with gambling all at the same time. This may sound like something you can't do because most of us earn very little, so when you are saving very little, or not even saving at all because you lack the funds, it feels like you should not gamble.
And you are right about that part, when you are poor then you should try to pay off your debts, and make new debt that will increase your income, that should be priority. However, that doesn't mean that we are going to be able to do whatever we want, it just has to be something that will get even better on the long run.