There are also deep cultural differences between Unix and Windows; how many people want to straddle both worlds? If you actually like Windows, wouldn't you want software that's Windows-like instead of stuff ported from Unix? The community is probably big enough now to support a Windows-specific open-source Web server.
And that server is not nginx. It is designed for Unix, it isn't designed for windows. The current apache has an arch much more amenable to running on windows.
