As I have said before, a lot of 'senior' artists still love the endless thrill of playing to a live audience, and are understandably reluctant to give that up.
Similarly, a large selection of the public want to see legendary performers, even allowing for the fact that their glory days are behind them.
I am selective - I can ignore the shaky voice, and absence of the high notes in someone like Paul McCartney, but I wouldn't cross the road to watch Axel Rose prostitute what is left of his talent galumphing around a stage with a bunch of session players and calling it Guns 'n' Roses.