Inherent problem with game design.
How do you make a meaningful character without it being the main character? Simple, you make a character that tags along, like Alyx Vance, Ellie, or Elizabeth! How do you make the whole game not a massive escort mission that the player has to suffer through? Simple, you make it so AI completely ignores them! How do we make it not frustrating that the player has to follow rules the AI can completely ignore? Err.... I don't know yet, but our game just sold 1 million copies, woo!