Because the material in question doesn't currently exist, not gathered in written form. Because my abilities may look effortless and instantaneous to you all, but I can assure you that they aren't. Because I'd like not to reach a point where I have to choose between generating another one of my passengers' endless requests and generating, for instance, oxygen.

[A telling pause; this is, perhaps, more than he'd intended to say.]

Thank you, Lieutenant. Carry on.