NPCs live to keep the main character well grounded in their setting. Each person is the main character of their own life, as cliché as that may sound — being an NPC is something seen from someone else’s main storyline, and we have no control over that.

To me, I’m the main character. To my children, they are — and I, hopefully, am the hero. To others, I might be the villain. No one is an NPC by themselves; if they are, then it’s someone who likely needs professional help.