LCARS isn't a graphical interface. It's actually a telepathic
interface that takes input directly from your thoughts and intentions and displays output accordingly.
The only reason it has buttons and panels is so that the user can push the button that corresponds most directly to the subject matter his thoughts correspond to, to make his workflow easier to categorize. The voice interface is supplemental to this and is used for general inquiries that are hard to categorize. Otherwise, the entire system simply reads your thoughts and uses the tactile commands to help you organize your own thought processes.