I suppose it depends. If a band has hired itself out to play weddings, bar/bat mitzvahs, graduations, etc. it should play what the people who hired them to play want them to play. Duh! That’s what wedding, bar/bat mitzvahs band do. That is the nature of the gig. On the other hand, if someone has hired a band, and these are probably people with money, because they like the specific band, like what the band does, then they should expect the band to be what it is and play what it plays. If you want something in the middle, something between a wedding band and your local cutting edge garage band, if you want your area cutting edge band to also play Reunited you that needs to be worked out in advance. But bottom line, it is up to the person hiring the band to be clear, up front, in advance about what exactly the job requirements are, just like when you hire anyone to do anything, I think. If the band can’t meet the job requirements hire someone else.