The one recent nominee who did engage with the committee on substantive issues was Robert Bork, who is also the one recent nominee to be voted down.
He chose to debate, and -- I think -- he chose it because he seriously believed he knew constitutional law far better than the Senators. But they knew TV better, and he was pompous and professorial. His belief in his own superiority showed. And people do not like the look of that on television. His notion that only people with thin records can survive the questions is another example of Bork displaying a superior attitude. If he'd just reined in that attitude and "taken the judicial Fifth" like everyone else, he'd have made it.
Descriptively, Althouse is probably right. But normatively, I think this is problematic. I'm not a Bork fan (I'm sure a lot of folks lost money on that bet), but I'd still wager that, yes, he really does know more about constitutional law than your average senator. They know TV--a useful skill, I guess, but one wholly unrelated (if not diametrically opposed) to getting an intelligent and qualified person into our judiciary.
Americans deserve to know who they are putting on the court. Questions on substantive areas of law matter, for the simple reason that no judge is a robot and all come in with preconceived biases and theories. A well-balanced judiciary thus let's these differing theories and ideas, the "jarring and discordant judgments" that "[j]udges of equal learning and integrity" might bring, be debated, argued over, hashed out, and balanced [Martin v. Hunter's Lessee, 14 U.S. 304, 348 (1816)]. In this context, asking and answering questions is essentially, but not if the very act of honestly representing your record becomes a political death sentence. Our judiciary (indeed, our whole political system) is not served well if to make it good a candidate has to do the Q&A version of "duck and cover."
I'm not sure that Bork should have been put on the Supreme Court, at least not so sure that I'd call his rejection a mistake. But the "lesson" we're learning from Bork may be worse than whatever he could have dished out as a Justice. It was the last to go, but now judicial candidacies join every other political office in that honesty is a liability.
Reasonable candidates, tough questions, fair consideration. Is that really too much to ask?