It was a huge political budget fight in the 90s. Clinton/Gore published a white paper detailing the threat of terrorism as the biggest threat to national security. They called for the fancy new detectors and what-not at airports.

The Republicans, who controlled Congress, said that the big threat was from nukes from unfriendly states (later dubbed 'the axis of evil') didn't permit the funding and instead increased 'Star Wars' funding (anti-missile tech).