Why? Simple.. you'll be strengthening the weaker side of your brain. I use my right hand to move my mouse and I am very fast and accurate with every movement I do. When I switch over to my left hand, my movement is sloppy... sometimes I hit the wrong buttons ETC. I know myself that I'm a left brain thinker so it comes as no surprise to me that my left hand is weaker/less coordinated. I over analyze shit and I'm not as aware as I'd like to be. Just switch it up so you are exercising both sides of your mind. If you want more information, check this. http://painting.about.com/od/rightleftbrain/a/Right_Brain.htm It's not 100% foolproof. You could be left handed and still be more left brain dominant or you could be right handed and be right brain dominant. It's still good to switch your position up because the left hand is controlled by the right brain and the right hand is controlled by the left. Exercise both sides instead of constantly using one side of your body/brain. Since we are all on the PC all day, might as well take advantage and switch up our routine for maximum benefit.