Windows 95 was a new paradigm, and people needed to learn how to interact with that system. Today, they already know how.
Microsoft understands that there has to be some changes. Eventually, the desktop/Win32 as we know it will cease to exist. But that day is still far away, and they need a new experience to replace it. Hence WinRT applications.
Microsoft cannot convince third-party application developers to move anything to WinRT if the Metro interface is not prominent enough to warrant the development effort. Microsoft would also have a harder time in the future at training users if today, they convince users that the Metro interface is some crappy application they can ignore (or, worse, that they never see in the first place to know it even exists).
Sometimes, you choose to do what hurts a bit now so that you don't experience more pain in the future.