Why it works and doesn't work? Win8 Scroll.

This comes to my attention and I am curious. In Home and All Apps, I don't have to use scroll bar to scroll with a mouse. I can keep moving to the right and it will scroll. But, that's about it. All the apps I have tried, Movie, Photo, SkyDrive, etc doesn't do this. They only support mouse wheel scrolls.

Is this feature limited to Home and All Apps only? Is this just an implementation? Meaning can I make my app scroll same as Home? How? And why doesn't Movie and Photo app doesn't support this? What's the reason they choose to not to support Home Mouse Scroll style in their apps?

Just trying to understand what's going on. If you know why, please share the insight, thank you.

The apps are still at an earlier stage of development than the OS.

I'd have hoped it would be an OS level feature and not something that would need baking into every app. Still early days, hopefully this will be addressed in an update soon.

@Michael Butler:

I guess there would be cases that you don't want to scroll by moving out of screen? Nothing comes to my mind. I do hope it is a default behavior for the typical scrollviewer.

I don't know.  That has to be applied very carefully to work effectively.  There are more places it doesn't work right that where it does, and it's really annoying to have things scrolling when you don't want them to.  With full-screen, single-screen Metro apps, it works better than something like a desktop app.  But even there, you have corner hotspots, and potential second monitor, simply bumping into the mouse, etc. that still create things to "reach for" and could trigger scrolling when you don't want it.  Within small controls it would be much easier to implement the scrolling without unwanted side effects.  It should be OS-supported behavior that is available, but default may not be the best thing.

Good call, multi-monitor will certainly cause issues.