Windows breaks horribly between upgrades. I know many people still using windows 7 because they're afraid to upgrade.
I remember this thread from last week too: https://news.ycombinator.com/item?id=13603837
It's "breaking" in the sense of compatibility. If an app runs on Win 7 and Win 10, Win 10 didn't break compatibility between Win7 and Win 10 because an upgrade doesn't go through properly.
And while I have heard plenty of issues with upgrades, I've also personally had 0 issues with them since 7, on any of my personal machines, even some in the insider track.
Even in the thread you link to almost every other response is in line with what I mean: "it's usually very very hard to accidentally make a program run on Windows version N but not on Windows Version N+1"