Candle in the Dark
When Iris stayed with the Vandals as a guest for the Vesian Revolutionary Front, she inducted Ves into the barebones essence of how neural interfaces worked.
It served one of the most important roles in a mech because they enabled human thought and machine processing to blend in seamlessly in a combined entity with an extraordinary capacity for information processing and decision making.
Humans by themselves made do with their brains and spine as the central nervous system that operated their bodies and gave them thought.
A mech can include all the raw processing power as its mech designer can manage to stuff inside, but without a good mind to operate the machine, most of its raw power would be wasted.
These days, AIs did a good job at serving as the basic brains of a mech, but skilled pilots were always able to leverage their creativity and intense practice to outsmart these dimwitted bot-like mechs.