That's how putting your savings into the market is sold, and it's true to an extent; you will lose out if you let your money sit around. But also, having a bunch of inattentive and unsavvy investors in the market is super convenient to anyone with a whole lot wealth. It means when the market crashes there's a cushion made up of your retirement savings. Plus, they have the option of buying low and increasing their share of the market. If you put all your money in an ETF for the long haul, you end up with a smaller share of the pie.

That's what really matters, right? Not absolute wealth, but spending power relative to other people around you. If the mechanics of the stock market increase this gap, even when people are bought in, I don't think that "enjoying the fruits of their labors" is the right framing.