You don't play a Vault Dweller (or descendant of one) but a courier, left for dead and saved by a friendly robot.
For some reason I didn't notice this the first time around. This is a glorious day, gentlemen. We are no longer MYSTICAL VAULT DWELLERS. We are now regular joes with crappy jobs who've actually lived in the wasteland. Don't ask me why, this is a lot more appealing.
Maybe, if we get really, really lucky, the quest won't be to save the world.