Pic unrelated. What is the purpose of gray matter (as opposed to white matter)? I understand that myelination is costly but other than that and considering the lynchpin to any success involving the nervous system - especially ones so dependent on the CNS as we - almost always requires myelinated neurons (tracts in this instance), I fail to see a benefit. Is it just a "we never needed to change it" thing?

TL;DR: why do we have to grey matter?