Aging sucks! Obviously you can do everything wrong, and mess your body up pretty good. You can also do everything right, and just have bad luck. Lingering injury, hereditary health conditions, things add up. By the time you are in your 60s, it takes a combination of good habits and good luck to be in good shape. It's comforting to point to active older people and say "I'm going to grow up to be just like them". Just aware of survivorship bias.