I would prefer that I have the right to cancel a performance if the performer is unable to give 100%. I would expect that a "professional" entertainer would provide me that option.
However, I have had several so-called "professional" artists show up sick an hour before the gig who gave mediocre performances.
The worst was an autoharpist who croaked through two songs in a 90-minute "show" and proved that even in the best of hands, about 10 minutes of autoharp solos was about as much variety as the instrument could offer.