At Disneyland, you are not just a customer service person, but a 'cast member.' You are there to behave almost like an actor. You are there to help the guests get into the spirit of the park.
Now imagine if we were all replaced with computer terminals and audio logs.
Not a lived-in one where survivors build community and vainly keep up appearances in the ironic 50s-post-apocolypse humor the games are known for.
I'd like to trade with human NPCs who make snide remarks about events that are happening or the player's faction.