I was about 12 years old when I heard a debate on the radio that prompted me to ask my parents why the debaters didn't answer the questions. Fast-forward 61 years and the names and faces have changed, but a politician's refusal to respond to a question with a related and meaningful answer remains unchallenged.
As long as moderators remain fearful of appearing overly aggressive or mindful that a candidate may start refusing interview requests, a dumbed-down society that is more enamored of sound bites and reality shows will continue to be satisfied with evasion and subterfuge.
In addition to posting the question on the screen to help the listeners be more aware if it has been answered or dodged, as Todd Rogers and Michael I. Norton suggest, the studio audience could be given a device with which to vote "answered" or "dodged" after each candidate's reply. Similarly, the TV audience could be given a phone number to call to report its reactions.