The logic is simple, you have two hands, left and right. When you buy a pair of gloves, it comes in left and right, one for your right hand and one for your left hand.
The some logic applies to everything you do, even in computer peripherals, your mouse and keyboard should come in a pair too, one for your right hand and one for your left hand. If your right handed, then you should get a right handed mouse, and a left handed keyboard so that you can control the mouse with your right and enter numbers with your left hand, this would also reduce the number of times your right hand have to leave the mouse to the numpad when you want to input numbers and reduce the distance your right hand have to travel between the mouse and the alphabet keys and distribute the control more equally between your two hands.
If you have two right handed peripheral, you're pretty stupid IMO. It's like wear two right handed gloves and shoes.
peace out.