Plenty of people are bothered about the the right buttons on a mouse, look at the FK2. It throws some people off especially when it becomes distracting.
Perhaps if they placed it where your pinky would never touch them it would be acceptable...
Only 10%~ of the world pop. is left handed, so in terms of cost/efficiency I can see why they wouldn't bother. They decided to optimize the mouse for the remaining 90% of the players.
Edited by Marctraider - 8/21/16 at 2:09pm