sigh...WinRT is a different operating system with a different underlying security architecture. It's not designed as a light-on-resources phone OS. One of the things everyone praises WP8 for is how lag-free and fluid it is, even on low-end hardware. While WinRT doesn't require the resources of Win 8, it certainly is a "heavier" OS than WP8. So running WinRT on, say, Lumia 620 grade hardware may produce an experience akin to the much maligned Android OS running on low end hardware - laaaaaagggggyyyyy.
Originally Posted by vish2801
Now you may want a full WinRT phone, and given some hot hardware it could work - and it certainly may have a place in the greater scheme of things - but WP8 certainly isn't going to BECOME WinRT and vice versa, though some underlying components may be shared between them. Basically WP8 is...a phone. WinRT is a general purpose computing platform. So the features and underlying security structures of the two are DIFFERENT.
So yes, Microsoft could CHOOSE to implement a general purpose file manager for WP8, but it's not as simple as just porting one from WinRT. Microsoft may well consider it worthwhile to perform some surgery on WP to include a general file manager at some point. Who knows? I think they'll find other ways of getting around the issues that people are currently complaining about.