I will occasionally see some of those bands who had their last hit record 20-30 years ago do a TV special or appear as part of some awards show. Seems like the vocalists don't have the harmony they had when popular and most of the original band members have been retired for several years and their replacements have turned over multiple times. Think most would be hugely disappointed seeing them in a live concert when the popular songs are now sung by other people and don't sound anything like what we remember. Paying top dollar for those groups would be a huge waste of money.
I don't understand the phenomenon of band member replacement. Just retire the band when most of the original vocalists have left.