You make a point, BUT, the same can be said for the entertainment industry.  Sports it most likely is the money, Golf, well Jack, Gary, Lee, and others, even Arnold was still able to play the game and people came, but that is Golf.  Entertainment industry you could say the money, but I think the attention they get, George Burns at 100, Bob Hope at 100, way past their prime and time, but could not walk away from the attention.  We don't walk in their shoes, today work force people are working longer, can't afford to retire but are they productive, defense would be what industry they were in.  I wish I could remember his name at The Men's Warehouse, a gentlemen was 75 that helped me, outstanding, ten years later I'm back and he is still there at 85, I like him, he was good.  The others helped him when he forgot something, but he knew the business and I would deal with him at 95.  Retirement, scary, to walk away, no one knows how to walk away or when to walk away, too many factors.