Because since Windows Vista all new APIs are COM based, Win32 C API is basically stuck on Windows XP view of the universe, with minor exceptions here and there.
Anyone that has to deal with Windows programming quickly discovers that COM is not the legacy people talk about on the Internet.
Game development for one, and there are still plenty of native applications on Windows to chose from, like most stuff in graphics, video editing, DAW, life sciences and control automation, thankfully we don't need Chrome in box for everything.
Your remark kind of proves the point Web is now ChromeOS Platform, as you could have mentioned browser instead.
Sure I mean, obviously the Windows API is COM based and has been for a long time. My point is, why seriously invest in the Windows API at all? A lot of APIs are only really being used by the Chrome team at this point anyway, so the quality of the API hardly matters.