Trackpads and touchscreens get the phone way of scrolling.
These feel like you are interacting with a piece of paper, so you move the paper around.
Mousewheels get the traditional way of scrolling.
Mice are more like controlling something.
It just is. Like F1-F12 keys are always F1-F12 keys, not the alt-function (like media/brightness etc).
I hate that Apple has called it "natural" Vs "reverse" in some psychological reconfiguring that you are going against the grain if you don't agree with them (as opposed to them changing the established standard).