Because cross-compiling binaries for Windows is easier than building natively
I want Microsoft to do better, want Windows to be a decent development platform-and yet, I constantly see Microsoft playing the open source game: advertising how open-source and developer friendly they are - only to crush developers under the heel of the corporate behemoth's boot.
The people who work at Microsoft are amazing, kind, talented individuals. This is aimed at the company's leadership, who I feel has on many occassions crushed myself and other developers under. It's a plea for help.
The source of truth for the 'open source' C#, C++, Rust, and other Windows SDKs is proprietary
You probably haven't heard of it before, but if you've ever used win32 API bindings in C#, C++, Rust, or other languages, odds are they were generated from a repository called microsoft/win32metadata.