When the environment is adversarial, smarter than you are, and informed about your methods, then in a theoretical sense it may be wise to have a quantum noise source handy.

It can be handy even if it's not adversarial, and even if it is equally as smart as you are but not smarter. Suppose you're playing a game with payoffs (A,A) = (0,0), (A,B) = (1,1), (B,A) = (1,1), (B,B) = (0,0) against a clone of yourself (and you can't talk to each other); the mixed strategy where you pick A half of the time and B half of the time wins half of the time, but either pure strategy always loses. This even though the other player isn't adversarial here -- in fact, his utility function is exactly the same as yours.