Why Hasn't MS created an App Store for Windows 7?

I am now a Mac user now however Windows 7 will always have a special place in my heart. That said, going back and looking at all my Windows 7 apps, on my bootcamp partition, I have a hard time finding any well designed Windows apps. Sure, I can find perfectly functional apps for Win 7 and they get the the job done but for the most part, with some exceptions, their ugly. I value UI and usability and I tend to spend my Money on not just apps that are feature complete but also have an attractive well design UI.

That said, why has MS not just created an App Store for Windows 7 like Apple has with Snow Leopard and OS X Lion? It wouldn't be a hard task as they have the infastructure, the know how and the experience to do so.

Its crazy to think that we have come all this way in computing without app stores. They provide a safe easy to use place for Users to buy and download apps (espeically with Virus/malware being such a problem for Microsoft) and provides visability, and an easy revenue stream for developers. With the successful Apple has had with the Mac App Store, I can't see why they would want to wait until Windows 8 before they want to roll it out.

Some the most beautifully designed Mac Apps I've downloaded have come from the mac App store. Sparrow and Reader are just fantasically written and I've yet to find a UI as nice on Win 7.

Microsoft has the Marketshare with Windows 7.... Adding an App Store would give huge app visability for developers.... and an app store would provide and easy to use revenue model for developers.

Marketshare + Visability + Revunue=competetion from developers which in turn creates better UI and features which makes customers happier.