Because it disables a person that CIA has spent years and countless $$$ training. Since symptoms are psychological, there no way to even prove that you did anything.
One person. That's an awful lot of coordination and risk and planning to pull it off for one guy. No offense, but he can't be that important. There's tens of thousands of agents in the CIA. He still has his memory, so it's not as if there's some secrets being protected there.
