Has anyone wondered why people say the show must go on?
Probably a rough copied analogy from actual show performers whom consider ''the show'' priority number one. There are cases where there are deaths within the cast/co-workers staff, and the show still continued because they deemed the show to be
that important.
Calling an event you dread (because of a recent other negative events) a ''show'' takes some of the edge off. And using it in the context of a performer, however emulated, boosts moral ever so slightly. Metaphors also have the tendency to sound somewhat funny; ''The show must go on.'' sounds a whole lot less negative then ''I really don't want to do this. But I'll do it anyway.'', also taking some of the edge of for the person you're saying it to.
But a better question yet, why is the phrase not applied when they bin yet another good movie/television show/theater performance? Apparently, the show does go on whenever enough money can be retrieved from it.