what do you mean where would the extra dialogue come from? they have five voice actors and every character seems to say the same worthless stuff anyways. i just thought there might be some random things for all the non essential characters to say, and they would spawn new ones from a random library of looks and names.....
Named npcs were made by the developers with certain traits, attributes and physical appearance. They aren't randomly generated like bandits as they have voices that match who they are and what they do even though the voices are overused.