Right back and left behind

There is a strange asymmetry between our uses of left and right. On the one hand, right back and left back are generally ‘value-free’ : they are labels for two positions on a playing field.

On the other hand, right behind and left behind are ‘value-laden’. Although both connote a position their meanings are quite different. Being right behind someone, indicates that you’re in total agreement with them, offering full support and marching in step.

Being left behind on the other hand indicates that while others have progressed those who are left behind feel abandoned or neglected. Is there a subtle difference in meaning between being left behind and being left out? I’m not sure. At root, another instance of the hegemony of the right?