Well if you think about it, your right brain controls the left foot and vice-versa. It goes for arms and legs too. I bet also most of those peoples are righty's when they write as well or lefty's.

The whole arm thing probably has to do witht eh fighting technique because, Drill instructor taught us some tai-jutsu and it seems less kick oriented than other forms and styles of fighting. The aerodynamic is a possibility, i don't know. But anyways I'm gonna ask him about it.