I think it has something to do with the human eye visually adjusting your aiming towards another player, differences depending on whether or not your gun is on the right or left hand side. Also I believe most right hand people are left eye predominant and therefore, will tend to aim a little to the left the majority of the time. If you didn’t notice, there are A LOT more right handed people then left handed people.

This is all theory of course… It’s a good as reason as any though… lol