Now you can affirm your status as a non-player character, there just to make things more interesting for the important people.
Are there days when you feel like you're just part of the program, that your actions are controlled by a mindless algorithm or Machiavellian gamemaster for the benefit of all the "real" players, who get to do all the exciting work and reap the ultimate rewards? (In other words, are you a non-management employee?)
Well, now you can subtly if not secretly display your disaffected outlook with the NPC shirt, which affirms your status as a non-player character, there just to make things more interesting for the important people.
The NPC shirt also has the added benefit of warding off unwanted interactions from LARPers, alternate-reality gamers, and anyone wielding a melee mug who might mistake you for someone worth PvPing for loot. That's protection you can't do without, especially during performance reviews or convention season.