[vacri]

much narrower arc from the current mouse position to the desired entry

Particularly since the top left option (in the easy-to-hit corner) isn't usually one that you want to access much in the use of a program. Sure, you can get your mouse in the vicinity, but you still have to hunt for the menu you actually want. If your screen(s) is large enough that this requires moving your head (or even your eyes significantly), it rapidly eats up any trivial advantage you gain from 'knowing where the menu bar is'.