Lindy, I think you're missing the point when it comes to those audio journals. Bioshock's plotting theme is all about interweaving the story into the actual gameplay experience in order to enhance the player's immersion, rather than just throwing some development into a straight-forward cutscene. That's why the journals are there. Most of them aren't at all crucial to understanding the overarching story, but they all enhance the ideas and themes set. You happen upon them like anyone else would.
Believe me, I'm far from a Bioshock cheerleader (*cough*Sklens*cough*), but that was one thing that I really loved in the game.