It is our brains that allow us to feel, memorize, recall and think. Without neurons to act as capacitors, diodes and transistors, the energy would be scattered in an unorganized way. How would a ghost be able to think? What ethereal circuitry exists that would allow for cognitive function? Do ghosts have synapses? Do ghosts have a frontal lobe? What about a cerebellum?
How would this ethereal circuitry maintain cohesion?
With precise instrumentation, we are able to detect gamma rays emitted by stars thousands of light-years away. We are capable to measure tiny electrical voltages at the near atomic level inside microprocessors. Yet we can't detect the massive amount of energy that would be required for a disembodied mind to maintain cohesion and interact with its environment?
If a brain (or a body) was not required to exist as a person, to think, to feel, and to interact with our surroundings, then why would nature gift us with brain-controlled bodies? Nature does not do wasteful things.