Not a euphemism. Yes you have higher variance in other fields (like tech) where you can become a billionaire. Car washes, by comparison, have low variance but reliably make mid 7-figures per year.
The market is super fragmented and localized so it doesn’t really matter how many other successful car washes exist. People won’t drive too far out of their way just for a car wash. This puts a ceiling on competition.
Starting a car wash is a big but not huge investment. This also puts a ceiling on competition, but remains accessible to fairly regular people. Starting a car wash also doesn’t require any specialized knowledge.
And because the business is profitable, but not that profitable, it has (afaik) escaped the clutches of private equity consolidation. This keeps money in the hands of local owners thus improving average/median outcomes and keeping variance low.