Good people do not, generally speaking, make good subjects for operas. Like the Greek tragedies that the sixteenth-century Venetian inventors of opera sought to recreate, Western musical drama has tended to be preoccupied with the darker extremes of human emotions: excessive passion and wild jealousy, smoldering resentment and implacable rage. These, after all, are the emotions that spark the kinds of actions—adultery, betrayal, revenge, murder—that make for gripping drama. Unpleasant as they may be in real life, such actions are essential to the Western idea of theater itself, in which the very notion of plot is deeply connected to difficulties, problems, disasters. Aristotle, in his Poetics, refers to plot as a knot tied by the author (he calls it a dêsis, a “binding up”) out of the manifold strands representing competing wills or desires or ideologies; an ugly and worrisome knot that will, in due course, ultimately come undone in a climactic moment of loosening or release of tension (the lysis, or “undoing”)—a concept that survives in our term “dénouement.”
There can, that is to say, be no theater unless bad things happen, unless there are terrible problems, insoluble knots; without them, there would be nothing for the characters to do. That “doing” gives us the very word by which we refer to what happens on stage: “drama” comes from the Greek drân, “to do” or “to act.” When we go to the theater, we want to see characters doing things. Bad things, preferably.
more from the NYRB here.