Philosophically, I think that people are rarely interested in talking too much about unknown unknowns because acknowledging them doesn't offer specific, useful

Philosophically, I think that people are rarely interested in talking too much about unknown unknowns because acknowledging them doesn't offer specific, useful predictions about the world - sure, you need to be aware that knowledge is approximate models, your thinking is imperfect, and be open to new data that clashes with your assumptions, but that general point is equally applicable to everything and therefore specific to nothing. Practically, I think that people are rarely interested in talking too much about unknown unknowns because it's typically a segue into talking about gods, or souls, or why quantum physics proves free will or something. Stuff that has been done to death a million times, is as empty as it ever was, and there is other cooler stuff to talk about.