system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we have an optic chiasm? Wouldn't it be simpler if the right eye supplied the right cortex and the same for the left?

I have found many descriptions of the optic chiasm yet I can find nothing for why it is there. Maybe it has something to do with 3D vision but I don't know enough to come to my own conclusion.
gpt
The left brain processes the right side of the visual field in both eyes, the right brain processes the left side of the visual field in both eyes. The crossing over of incoming visual stimuli and the location that this splitting/mixing occurs is the optic chiasm.

It's difficult to ask why sometimes in medicine - it isn't like we have an owner's manual to refer to for a definitive answer. 

One explanation might be that this set up is safer. If you sustain trauma or receive damage (stroke, tumor, lesion) to your occipital lobe or optic radiations (or other associated structures) on only one side of your brain past the point of the optic chiasm, you have not rendered one eye totally useless, instead one half of the visual field has been wiped out. Your binocular depth perception remains functional.