[kazinator]

If Lisp had been invented in Japan, maybe the main connective of an expression would have ended up as the last item visually: (1 1 +). Maybe.

However, it would still be the first element of the list in the abstract data structure: i.e. the equivalent of (car '(1 1 +)) -> +. (Or, rather, of course, ((1 1 +)' car) -> +. Let's use the fantasy read syntax.)

The main point is not that + is leftmost or rightmost, but that it's at a fixed position in the data structure, and that it is the first/most accessible position.