Joystick-left buttons-right wasn't "standardized" until about Street Fighter II (call it after 1990). I had friends who were joystick-right players, that left the scene after most of the joystick-right & joystick-middle cabs got converted.

Playing with their arms crossed was Not Cool.
I've heard that CPs were going joystick-left before that, due to nintendo's gamepad, but one of the things about arcades was its stuff were
far better then consoles (back then). Dumbing down arcades to console level would not be good marketing. Even most two player games had buttons on both sides, until SF2 and it's 6 buttons.
Me, having grown up in the days when joystick middle was the norm, I prefer to play some random games joystick-right, even though I usually like the now standard joystick-left.

BTW, the joystick-left is "standard" only in digital inputs; flightsticks are still usually stick-right buttons-left.
edit spelling