Right back, Left back, Right behind, Left behind

The other day I was struck by the 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, right behind and left behind are ‘value-laden’. Although both have position connotations, their meanings are quite different. To be right behind someone, indicates that you’re in total agreement with them, offering full support and marching in step.

To be left behind (in the current climate) indicates that while others have moved on those who are left behind feel abandoned or neglected. Is there arsubtle difference in meaning between being left behind and being left out?I’m not sure. Another instance of the hegemony of the right?