Well... It's mostly due to how tightly integrated the whole Xcode+iPhone is, It'd be a difficult job for Apple to make it work on Windows for a few reasons:
1) No "Uniform" IDE, sure you could do it in Visual Studio, but you'd have people whining, wanting it for x IDE
2) They'd end up needing to port the iPhone Simulator to Windows, which would involve basically... redoing Cocoa/Cocoa Touch for Windows (A benefit to this, would be they could offer applications that would compile in Windows + OSX with minimal recodoing)
3) A vast majority of Windows developers have no ****ing clue about Objective-C (due to it being irrelevant to them), making it a very small minority, creating a result which makes less money than the effort (and costs) needed (unless they ended up charging an extortionate fee [thus cutting out more developers], making even less people using it, creating a vicious cycle.)
There's just a few reasons I can see why they don't open it up to Windows, mostly relating to the Language, and the tight integration with Native OSX frameworks/libraries.
1) No "Uniform" IDE, sure you could do it in Visual Studio, but you'd have people whining, wanting it for x IDE
2) They'd end up needing to port the iPhone Simulator to Windows, which would involve basically... redoing Cocoa/Cocoa Touch for Windows (A benefit to this, would be they could offer applications that would compile in Windows + OSX with minimal recodoing)
3) A vast majority of Windows developers have no ****ing clue about Objective-C (due to it being irrelevant to them), making it a very small minority, creating a result which makes less money than the effort (and costs) needed (unless they ended up charging an extortionate fee [thus cutting out more developers], making even less people using it, creating a vicious cycle.)
There's just a few reasons I can see why they don't open it up to Windows, mostly relating to the Language, and the tight integration with Native OSX frameworks/libraries.