Because I think it's best to shield the judiciary as much as humanly possible from the political posturing of Congress. I don't think we want them thinking, even in the far reaches of their subconscious, "Christ, what if Congress rakes me over the coals on national TV for this?" Judges should be making their decisions purely based on their interpretations of the law, and nothing else.
If you don't like the way a judge ruled, that's what the appeals process is for. If the law, as interpreted, isn't working, then pass a new law or start the amendment process. The only people who will benefit from dragging them in front of Congressional theatrics are spin doctors and campaign managers.