Cause there's no point in doing so. [ he responds, in a tone of "well DUH." ] Isn't that obvious?

[ No, it is not obvious in the slightest. The Doctor leans back in his chair slightly as he looks over at Mark, continuing that "well DUH" tone as he speaks. ]

You obviously feel of two minds about this--don't be, by the way, there's absolutely nothing shameful about learning. What would I do, tell people just to rub it in their faces? I'm not that petty.