Also if currently you are probably running Windows 8 on a virtual machine or luckily on a computer, there is not any doubt that this new operating system and especially the metro-style interface is dedicated to touch enabled devices like tablets. The plans of Microsoft infact include the new WOA keywork where the acronym stands for Windows On ARM that is the aim of making available this interface on a wide set of mobile devices that currently embrace this successful processor architecture. Running on a tablet does not only imply a different input interface like the touch screen, but also it requires a careful use of system resources that are not always large on this kind of device. This is the reason why metro-style applications have an application lifecycle that is mostly similar to the Windows Phone than of classical desktop apps.
I'm sure many users leave applications open on accident without saving their work, this would provide an opportunity for the application to save state. It's true that there's nothing stopping most applications from having autosave features today, but with the chance of the application being suspended, it sort of forces developers to add this functionality.