The 3-act structure is an old principle widely adhered to in storytelling. It can be found in plays, poetry, novels, comic books, short stories, video games, and the movies. It was present in the novels of Conan Doyle, the plays of Shakespeare, the fables of Aesop, the poetry of Aristotle, and the films of Hitchcock. It’s older than Greek dramaturgy. Hollywood and Broadway use it well. It’s irrefutable and bullet-proof, so to speak.