Perhaps it is reasonable to expect a white-collar worker to work past 65, but how about a blue-collar worker or a laborer? Not everyone sits in a chair in front of a computer all day for their job.
Even for white-collar and computer people, intellectual abilities do degrade over time too. If the task is demanding in that respect and you go below the threshold where it cannot be compensated by experience, performance will drop dramatically to the point of not being able to accomplish the tasks in a reasonable way. Of course the degradation rate and acceleration depend highly on the individual. But you cannot ask everybody to work these jobs after 65 or 70, even though these are white-collar jobs.
Not sure why downvoted - there are people who stay mentally sharp until their 80s or 90s, and everybody keeps talking about them. These are rather exceptions. Most people suffer from slow mental decline, I could see it on my grandparents and their peers. That is, if you are still OK and not crippled physically or mentally by some accident/disease.
It seems that for most healthy, after 70 body goes down the drain too. I cannot imagine myself doing same software dev work at this age, all the bullsh*t and pressures that corporate jobs contain would make me leave on my own.
My plan is to retire earlier (60-61), not later! Enjoy the world, life and freedom of travel while there is still some strength in the body. I don't get why anybody would want to work more than necessary (unless your job is your hobby, but that is true for very few)
