In fact examples like Windows CE (Now WP8) prove you wrong.
[1](http://en.wikipedia.org/wiki/Windows_Server_2008#Server_Core)
Please give server core on Windows Server 2012[0] a try. They could use your feedback.
[0] http://msdn.microsoft.com/en-us/library/windows/desktop/hh84...
> "Server Core is a minimal server installation option for computers running on the operating system. Server Core provides a low-maintenance server environment with limited functionality."
Limited functionality is the key. In order to administer windows server, one is expected to use remote desktop. This is in contrast to a unix machine, where everything can be controlled via command line and configuration scripts.
It is getting better, as Powershell exposes a lot of functionality. But it is still not there yet.
It's actually how Apple built iOS, too. But will they put WP8 on tablets? No of course not. Instead, they'll try and push Windows RT to phones, which is the totally wrong way to do it. But just watch it happen.
Apple were able to rip the top layers off OSX and ship it as iOS without too much trouble, because it's unix. (They didn't start from scratch.)
Windows, not so much. MS have been trying to do it for a decade or more, and they've failed for the reasons outlined by optymizer.