As has been said before, the effects of ageing are different for everyone, and you can't say that just because Springsteen can still go out & do powerful, long shows that everyone should be able to. Mark has made the wise decision to stop touring at the right time, We knew when the DS classics with "twiddly bits" were dropped from the last tour that things were getting worse, but he was still able to deliver a great show. Now, 5 years later he will know he couldn't do it again. Much as I love McCartney, I think he should have stopped touring a while ago because his voice is going, I think it's better to bow out with dignity at the right time, and that's what Mark has done.
I'm 68 and I can no longer manage to play TR or ToL, my fingers are getting stiffer & I've a hint of a tremor (essential tremor).
I hate to think what bashing those classics out on extended tours must have done to Mark's hands and I remember him wearing a wrist brace early in his solo career so he's probably suffering from years of heavy playing as much as any ailment.