Keep in mind that neurosurgeons and people who study the brain are looking for things that they can measure. The mind cannot be measured since it has yet to even be properly defined. Is it just a bunch of neurons and cells or is it more than that? You're right that we seem to use all of our brain (the organ) and we can see that utilizing cat scans, mri's and the like. But I don't think anyone has managed to define or measure the mind or psyche.