Not a "toy", just "specialized"
WinRT is aimed at the needs of tablets, and you really don't need to do those things on a tablet. Tablets are designed to "just work", and when apps get that access, they do things that break devices. Just look at Windows! How many times has a rogue app made the whole system unstable? With the tablet model, you really don't need apps to have that access. No defrag? Who cares, with a tablet you aren't going to be putting enough data (or the kind of data) locally for it to matter. No registry editing? Good, the last thing I want is a trashed system anyways, apps should use their own, isolated configuration and that's it. No access to the system files? Great! Because if an app has a security exploit in it, wouldn't you rather that it not have access to that stuff? Etc.
J.Ja