Because HNQ isn't about how broadly applicable a question is, not really. It's about how incendiary and 'exciting' a question is (to get users to click through and explore other sites in the network), and that often comes from controversial issues (at least in the area that the questions are relevant to) like gun control, which is why there's been controversy over HNQs for years.
Also, to be fair, 'broadly applicable' is a bit of a misnomer when it comes to SE: how many questions from Math Stack Exchange or TeX and Friends are 'broadly applicable'? Most people don't really care about TeX (sadly), so it's really much more about what's the most interesting and the 'best' of each site, or at least, that's what it's supposed to be.
Users are supposed to see an exemplary question from a particular site, go through, and think, "Oh, I should join that site - that's interesting and well handled." Of course, as I noted, it doesn't generally work like that.
Also, since there was an edit: HNQ status is assigned by an algorithm that looks at upvotes and views, among other things, not by a human. Due to some more recent controversy, moderators got permission to manually remove HNQs from the HNQ listing, but beyond that? It's an algorithm.
Finally, I think that the question about SE being a global enterprise kind of misses the point - if it's a global enterprise, there'll be questions applicable to all sorts of different specific parts of the world. It doesn't mean all questions will apply everywhere. Unless it's math, of course.