Manufacturing, farming, fishing, etc were much more common industries for those who are now 85 than it is for those who are now 55.
There is a huge difference between retiring from manual labor at 60 after having worked from you were 15 and retirering from a desk job at 65 after having worked from you were 25.
Then take into account that they used to work Saturdays, that they used to work more hours per day, that fewer had recognized disabilities, that fewer received welfare, that they had much less vacation, that women had more pregnancies and that those of them that worked had shorter maternity leave.
The 'lucky' old had worked more and physically harder at 60 than we will have at 70.