A philosophical perplexion has been why mirror images correct vertically but not ipsi-contralaterally.
A possible answer is that this is an incidental neurological hard wire which is in place to determine bilateral symmetry – that is to say to determine a comparison between left and right. It is common, of course, to do this, and quite easy to do (although sometimes emphasised by tricks using a reversed photographic half-image).
The importance of this capability is that sexual attraction / selection depends heavily on facial (and probably other body) symmetry as a prime guiding factor.
Whether a symmetrical individual is more “healthy” or has a more desirable gene construct for evolutionary purposes some could debate. Nevertheless the enhanced attraction of isobilaterally symmetrical individuals exists, which could not be assessed without a sophisticated neurological mechanism such as this