Just started reading Sue Blackmore's new book: Conversations on Consciousness. Great introduction - but I have stalled already on Q2 of the 1st conversation - Baars. He says "the primary function of the nervous system is to encode knowledge...".
Brains are control systems for bodies. Pretty amazing control systems of course, but control systems all the same. Bodies have sensors (senses) and actuators (muscles). In very simple animals the outputs from the senses are almost directly connected to the muscles, so that the animal always reacts reflexively to stimuli. More complex animals have more brain in between senses and muscles and so may deliberate before reacting. Of course even very complex animals still have reflexes - think of the classic reflex test on your knee.
Of course I accept entirely that complex brains do encode knowledge, probably in a multiplicity of ways some of which we can discern - like the apparent spatial mapping of images into the visual cortex - but many ways that are not (yet) at all understandable.
But that is not what they're for.