They are. I'm playing the new Assassin's Creed right now, and as you explore the city of Constantinople you'll run into landmarks and people, each of whom have an in-game encyclopedia entry that you can quick-key into. It doesn't have anything to do with gameplay, and is merely there to satisfy your curiosity. The dialogue and story also make an attempt to communicate the political and economic intrigue of the era.
That and it takes place in a specific period of history that also touches on many famous people in that era, albeit fictionally. I have to say, every time I play an AC game I end up reading Wikipedia about the real-life people, places, and history that it depicts, because it's just so damned interesting.
I can't be the only one. But it certainly beats most "educational" games that smack you over the head. "Now, who can tell me when the Byzantine Empire fell?"