Hey Setch - this is actually one of my features so I can explain in detail
You’re right that in the physical world you usually don’t get visual feedback. You do get other types of feedback (tactile in particular) that we lack on today’s touchscreens. This feature attempts to use visuals to make up for the lack of tactile feedback.
The other thing we put a lot of time into is making it so the feedback is very subtle (barely noticeable) when you are touching the system in a ‘correct’ way (tapping a buttong, scrolling within the bounds of a list, etc). The feedback becomes more visible (both size and duration increase) when you touch ‘incorrectly’ (trying to resize something beyond it’s max, tapping or dragging on the background of an app instead of interactive control, etc.) So it’s out of the way for expert users but for novices it lets them know “yeah, this is a touch screen. here’s how your touch is interpreted. try touching something else now”
Then for specific controls we put extra stuff into the visuals to make them communicate other info in a passive and contextual way (the exact point for a finger that we use for hit testing, the max size of a scatterview item, the bounds of a scrollviewer, etc).