I think that w are a bit harsh on them. They are musicians, devoted their lives on playing these songs, they have to make a living and they love what they are doing and there seems to be an audience to pay to see them . Seems to me the ideal combination. If one of the reasons above is eclipsed the thing will fall apart. The same with Queen. I liked them from Sheer heart attack until Jazz and then they had many great songs during the 80ies, and their last proper album was amazingly good. And then some of them thought that they were equally Queen without Mercury (they were correct) and some of them thought that the Queen is dead (equally correct). Now I believe it has to do with the ones paying to see them. As long as there is a demand, some of them will cover it. No harm done really. It is only a matter of taste. I would never go to see Mick and Keith, because there is nothing there for me, (Bill Wyman could be an example for your case, though) but I won't say no to our MK, playing his DS songs, as well as the new ones.