You are correct that the traits are guidelines for resolving NPC interactions. Its more of an add-to the existing game framework than a necessary system for people to use.
I included Traits to provide a system for resolving person-to-person interactions (NPC and player) that I always struggle with when playing solo or cooperatively without a GM. Players are the main characters of their story, so keeping roles one sided simplifies things and keeps the players locked into their decisions and progression.