I would dispute that line of thinking. Wealthier people who are used to getting what they want when they want it would have worse impulse control. Poorer people are used to having to wait already.
Past a certain level of desperation, there can be a hard-to-escape level of nihilism - "why bother saving, something's going to take it and I'm going to be fucked tomorrow no matter how much I do". Whether this is an accurate description of the situation or not is going to depend, but I have met a number of people who think like this even when they've not been that desperate in decades, and it bites them as soon as they stop making so much that it masks the problem.
And in some cases, it can be practically true - there's various systems that are designed with nasty edges where if you have enough resources accrued, you stop being given support, but the thresholds, by design or incident, are far below the point where you might be able to escape the pit, so you can't save your way out of it - you'll suffer a catastrophic penalty for accumulating wealth, and then be worse off.
Once you get past a certain level of instability, you start seeing gains again from saving if you do it, but not necessarily immediately - after all, if you're earning $9 an hour, at perhaps 160hr/month, and you're spending $800/mo on rent, that's $640 ignoring taxes to spend on anything else, so even if you somehow spent _none_ of that on taxes or food or w/e, it'd take more than a month to save one month's rent. So the benefits of saving are slow to accrue, when your income is not much past your expenses, and it can be hard to convince someone who's never had that level of safety and stability that it's worth it when it's going to take a long time to be worth it.
If your income is outsized enough to your expenses, then it can be more obvious much faster, _but only if you've ever had to think about it_ - if you've been externalizing your life expenses to your parents or a trust fund, it's even more foreign to you than the people described above who have concluded saving isn't useful, because you've never had to think about money as a resource in your life, it's just a thing you spend unendingly.
