Sorry, just in terms of flying, I STILL can't see why Airbus put the sidesticks literally 'one side or the other,' rather than between the knees.
Assuming you are sitting at a desk, place your right hand directly in front of you, centered on your body. Unless you are deformed, your arm will be at nearly 45 degrees relative to your chest line. Tip your hand forward/back, turn it side to side.... get it? Every axis is 45 degrees off what would be the nose of the (imaginary) aircraft.
Now take your arm and position it at the most natural position on the desk to your right side, probably just about where your mouse sits.... look, everything is now more or less orthogonal with the imaginary aircraft.
Repeat with your left hand... in the center position the axis are now 90 degrees offset from before - i.e. to pulling back on the stick is now operating in an entirely different direction than it was with the right hand...
Now you can argue that the central joystick should be oriented fore-aft/left-right on axis with the aircraft, but now you are inducing a very painful twist to either arm, and the stick movement is no longer in-line with any of the arms natural axis.
That is why. Airbus are not dumb.