Why didn't anyone understand why Addiction is a copy of David, and they just decided that it's an alter ego, even though an alter ego is a person's second self that is created to overcome their fears or protect themselves. For David, this dissociation defense from the fact that he’s an addict — meaning someone else is to blame for the addiction, and he simply "caught" it, like a physical illness; essentially, that’s why the Addiction is so aggressive. The theory that he just created an alter ego and it got "angry" or "mad" is nonsense, because an alter ego can be controlled, and there's no hint of DID or OSDD in the game.