Answer: I would say it's because there is so much about the brain that we don't know about yet, it's harder for us to understand certain illnesses and dysfunctions because of the sheer complexity of the organ and the role it plays in our own existence. It's easier to understand an organ such as the pancreas because while both fragile and complex, it is not nearly as mysterious as the human brain and doesn't have even nearly the same range of function.
Explanation: