There's an enormous community of people who spend all their time worrying about the contents or behavior of Windows binaries. I've met some of them through my work, like malware analysts who deal with malware that's part of phishing attacks. The phishers will often prefer to create Windows-only attacks because Windows has such a commanding market share lead among most populations of phishing targets; in turn, that's what the people trying to defend against or mitigate those attacks will study. To folks in that sort of field, "binary" is virtually synonymous with "Windows binary"!
I guess also historically most of the tools for creating, modifying, and examining binaries for a given platform have been native to that platform, rather than cross tools. That's surely because most people (with the exception of embedded developers) do much more native development than cross development. I can get a small number of packages on my Linux machine that will deal with Windows executables in some relatively shallow way, but I have tons of programs already installed that do complicated and specific things to Linux ELF binaries even though I don't typically use those programs on a day-to-day basis.
