It’s true in theory, but a couple of big things happen 1) for the vast majority outlays increase as fast if not faster than wealth, and 2) things like divorce/remarriage/second families happen creating massive dilution, 3) the experience of most HNW clients is more like 3-5% real after tax.
Yes I suspect the rich's strategy of owning nothing and controlling everything contributes as much to their wealth retention through the inevitable catastrophic events in life, as much as snowball interest accumulation does.
Middle class / poor people generally know how to build wealth through interest but make the fatal mistake of keeping their wealth largely tied up in on-paper assets in their name, this means they're ripe for the taking from every judge / wife / healthcare creditors / random guy with a lawsuit as soon as something in their life goes south. Of course once you get to a certain segment of underclass people who are basically unbanked you get back to horse-shoe theory and you'll never be getting their $50k gold chain they keep around their neck.
