Because the goal isn't an unbiased review, but a stamp of political approval? Did you really think the government as a whole is self-critical? Read Feynman's a

Because the goal isn't an unbiased review, but a stamp of political approval? Did you really think the government as a whole is self-critical? Read Feynman's account of being on the Challenger review panel. He was the token scientist among politicians and PR people, and they tried to steer him away from doing any actual investigations. They tried to agree, before doing any investigation into why the shuttle blew up, not to blame NASA and to indeed give it vote of confidence. The goal is to deflect blame from the government while making the status quo look hunky dory. Any actual investigation is counterproductive and I guarantee it won't actually happen to the NSA. This is a PR campaign, period.