HN and /r/programming are great resources, but they're not by any means representative of developers or the programming world in general. Indeed, I think it's quite safe to say the vast majority of developers have never heard of HN (or even Github) and while they might know of Reddit most of them probably don't visit. This might be a lamentable thing, depending on your views, but it is what it is.

It's really easy to get caught up in the SV culture, but it's by no means the rule. There's millions of developers out there whose code is never made public, writing Java, .NET, C, C++, Ada, Fortran, and other languages that HN would regard as obscure, niche, or dead. They're consulting or working for small businesses, medium size businesses, enterprises, local, state, federal governments.

I don't know if most of them use Windows, but it's definitely a hugely substantial fraction. It's not a small minority.