The government basically invented the notion of "retirement" in the first place, too, though. There was no historical precedent for just stopping working before you physically couldn't anymore, in which case you generally died very shortly thereafter.
At the time U.S. social security was invented, the age at which you could draw benefits was higher than the average life expectancy, the thought being, "Well you've put in as much good work time as most people do when they die, so if you live longer than that, we'll take care of you."
This whole notion of a decade or more of "retirement" being totally normal is extremely novel, and I'm not at all sure it's good for people. Is it good not to have to do physically demanding work when you're 70? Sure. But as a culture, we would benefit an awful lot from learning from elders in advisory roles, if we didn't idolize the innovative flash-in-the-pan-probably-won't-work-but-let's-try-it-anyway startup mentality.
