It’s simple actually, this is one of Ive’s design obscenities. To make room for a lightning plug at the top of the mouse you would have to change the “perfect”

It’s simple actually, this is one of Ive’s design obscenities. To make room for a lightning plug at the top of the mouse you would have to change the “perfect” symmetrical shape of the mouse. Disabling it when upside down is just a good way to avoid accidental input while upside down or balanced on its side from annoying the user. All of it simply stems from the “design first” hardware design ethos of Apple under Ive’s reign as head of design.