Yes, I've heard that one, but I doubt it is true. Firstly many people over 80, particularly if they stay fit in mind and body, lead lives that are just as busy and active as much younger people. Secondly even if you stay fit you may well find that you havent the energy and flexibility you had and would like to get others to do your cleaning, grass cutting etc. If in later life you do suffer some disability you may need even more help and help of any kind is expensive and Social Services won't support you unless the lack of care threatens your life.
I suspect that many of those over 80 need larger incomes than those under that age to pay for any help and assistance they need