I remember reading about this in the past. Someone was proposing the Israeli model of airport security as an effective (in a country where you're much more likely to come across terrorists and bombs than in North America) way of implementing security, in place of what the TSA currently does.
I think the difference is competence: the Israel security agents relied a lot on common sense and instinct, but with the kind of people the TSA hires, you have to, instead, provide stricter guidelines and reproducible processes. And that's where such a security method fails, because it has to rely on the experience, instinct, intelligence and common sense of the security agents.
Better to throw $900 million down the drain than to offer high enough pay to attract the kind of people this security model requires.