Because growth for its own sake is antithetical to the HN mission. There is no money making off this site, it exists for people of a like-mind to socialize and learn. If you want growth for it's own sake, go talk to reddit.
I'm here for technical content. Occasionally that overlaps with politics, frequently there are other things that most technical people will be interested in, but primarily, I'm here for technical content.
This post should be of extreme interest to absolutely everyone, without exception. And it's exactly that complete generality that makes it inappropriate, in my view, for a technically focused forum such as HN.
My view is but one among many, and others may disagree, but if HN loses focus, it loses appeal to me, and to many of those whose opinions, ideas and comments I want to see.