I think that's about the typical life span of a modern car, too. Anything older than a decade tends to be quite an awful drive. Unless it was built in the days before we decided everything needed to be so expendable.
https://www.statista.com/statistics/261877/average-age-of-pa...
It's true they don't look great underneath...
Stop buying bad cars.
Conversely, there are many engines on there noted for their reliability, Ford Modular V8, for example, GM LS1, Ford Model T engine, VW Air-cooled Engine.
Don't forget, just because a typical owner may sell a car after 5-10 years, doesn't mean it goes away into the aether :).
[FWIW, I have a 2004 Subaru WRX; I make the dealership rounds every year looking for replacements, and cannot find anything that handles better in that price range - in fact, by all accounts modern WRXs are a softer drive]
A long tail on only one side (no car has a negative age) means that more than half would be older than the average. You were thinking of the median, not the average.