2. Because their company has standardized on Windows desktops and/or hardware.
3. Because some people might actually believe and have good evidence that Windows is a more "developer friendly" operating system for their needs.
OS X just doesn't cut it when it comes to keyboard shortcuts and window management... Linux is nice but lacking in stuff not related to development.
Also, I think Windows has (or had, depending on preference) a great GUI and a dismal CLI, while _nix is mostly the other way around.
I prefer Apple hardware, but I'm not exactly a fan of being bound to it.
It seems a little arrogant to assume your specific hardware requirements are everyone's hardware requirements.
While I am actively infecting my org with FOSS, those of us working in corp land are often forced to use a Windows box behind an NTLM proxy and are blocked from installing vbox.