I'm not sure why you'd call it the most ‘natural’ form. Scroll bars don't appear in nature. Of all the ways to scroll content, direct manipulation (dragging you

I'm not sure why you'd call it the most ‘natural’ form. Scroll bars don't appear in nature. Of all the ways to scroll content, direct manipulation (dragging your finger directly on the document on the screen) is most like the way we move real things around in nature.