The Senate confirmation hearings for a Supreme Court Justice play an important role in a new Justice's education: they underscore, for the good of the nation, the fact that Congress is chock full of idiots and assholes who like nothing better than to hear their own voices. They divide the world neatly into good guys, to be supported at all cost (but tested rigorously for ideological purity!) and bad guys, to be torn down at all costs.
This is important, because otherwise Supreme Court Justices might be tempted to respect Congress, to consider Congressional approval a thing of consequence, not to be overturned lightly. Thank goodness the Senate takes the time and effort to disabuse any crazy ideas of Congressional competence or good faith before those assumptions might do damage!