These things have been in Apple ever since the original Macintosh. In that case it was 'one mouse button, so simple'. Except to make the system usable as other systems with multiple button mice, they added a whole load of keyboard shortcuts mimiced how the multibutton mice worked, which ended up being far more complicated than just adding another button to the mouse.
I’m fairly sure they got rid of all those other buttons because for the majority of customers they created more confusion than power back then.
Also, speaking as a power user who’s also a southpaw, I’ve got more than a few choice words for many of the multibutton mice I’ve had to use over the years. Apple’s late ADB mice were lovely in the hand and completely unprejudiced.
