That's the point. It doesn't always happen. I mean if you were to ask people who started the Cold War, you could start a flamewar over that and there's people still living who remember that (not many, to be sure, but some). Most people could give a pretty fair version of the Roman Empire or the Han Empire, but that's partly because time has passed to the point where unless you're a Turk, Russian, or *really* reactionary German nobody gives a shit who's the right successor to the mantle of Caesar Augustus.