But when you move a switch like the ones demonstrated here in the real world, you have the haptic feedback of moving the pin physically, of it "snapping" into place. And that's how you know that your switch toggling was successful.

The "digital switch" does not have that. You usually don't even "move" it, as in "move the finger over the screen", but you just touch it. And your finger obscures the UI component in the moment you touch it, without any haptic feedback (except for your finger hitting the screen somewhere, but that does not necessarily mean that the switch has toggled). The animation replaces this missing haptic feedback, by your eyes seeing the switch moving, when you remove your finger after touching the screen.