To the extent that consciousness is useful, it is useful in small quantities, and for very particular kinds of tasks. It's easy to understand why you would not want to be consciously aware of the intricacies of your muscle movement, but this can be less intuitive when applied to your perceptions, thoughts, and beliefs, which are also final products of the activity of billions of nerve cells.
Want to know more about the inner workings of a neuroscience lab? Watch a video profile of David and his students on NOVA Science Now.
Your reality need not be constrained by your biology. Read the interview here.
Want to know how neuroscience will force major changes in our criminal justice system? Read David's article The Brain on Trial in The Atlantic. Now anthologized in 2012 Best American Science and Nature Writing.