The non-app memory appears to be mounted as /sdcard/. which is where all of the data seems to be stored. When I look at the app memory usage, it doesn't differentiate and shows a large amount of space free, so I am guessing that the OS automatically uses the /sdcard/ location if available for anything that can be stored there... and therefore no need for the app, especially since there is no external SD card.
Things seem to have changed for Android with the advent of devices with larger internal storage, as my Samsung Galaxy Tab 2 does use external SD cards, which many apps don't seem able to access, since it is mounted as something like /extsdcard/ but this may be vendor related and not Android in general.