A lot of the people in the tribute bands aren't necessarily fans of the music.
Most of them are just hired musicians or even sometimes even the "owners" aren't fans, just people that like the money they make with the tribute
Personally I prefer tribute bands where at least the leader is a fan, it adds a piece of love to the tribute that makes it more honest that just milking the cow but, if the attendance enjoy it, good for them, that's what's important in the end, because everyone has to work to pay the bills.