What effect does the repetition in Macbeth have on the play?

Why has Macbeth been adapted so many times?

A. The acts of violence and murder in the play are often considered old-fashioned by today's standards. B. Audiences enjoy plays in which a person in a position of power goes insane and is killed. C. Elements of Macbeth's ambition and dark rise to power are often seen as relevant to many modern-day situations. D. Modern-day playwrights are interested in changing the plot of the play to engineer a happier ending. It is a great play that is popular with audiences, so when theatres want to bring in money, they will put it on, but they also want to attract audiences that have seen the play before, so they put a new spin on it.