The owner's manual doesn't have any information on whether this is switched or always-on, but my suspicion is that it'll be switched with the ignition; too many opportunities for trucks to kill their battery or burn down if somebody forgets to switch something off otherwise. I'd imagine it'd be a good power point for a powered bed crane if someone had need of one for a small shop truck.
I have no idea what I'd use it for, but it's good to know that they're there if needed.