That’s interesting! My mind always just assumes the reason is some “core” biological reason. I think contralateral wiring helps the brain manage signal sequencing while preserving evolutionary symmetry.

The spinal cord handles rapid reflexes (pulling away from a hot stove), leaving the brain for slower non-immediate tasks. By crossing nerves before they reach the brain a standardized delay is introduced, giving the brain a predictable offset to filter against. The optic chiasm follows the same logic.

And I think this is necessary to keep same-side brain-body pairs from over-optimizing (direct nerve connection from the right hand to the right brain hemisphere) their paths at the expense of balance, preserving biological symmetry.