Part of the issue as well was that the Patriot was pressed into a role for which it wasn't designed. The surface to air mission has historically been a low priority for the U.S., and Patriot was the first real SAM system since Hawk to be designed from the start for the anti-aircraft role. In '91 it was suddenly pressed into the ballistic missile interception role, (which had been explored a little earlier in the program...but to say it was green is an understatement.)

The Gulf War forshadowed the issues that snacktime so well described earlier: Cheap rockets, artillery, and missiles being used against urban targets would, and will continue to be a problem to be solved and require countermeasures for. But for the army that was deployed in '91 was designed to fight a ground war in Europe, not revenge attacks and Scud potshots in the middle east. It worked to assuage fears at the time, and that was good enough.

Don't think that those lessons were ignored, however. Systems like Arrow and Iron Dome were developed not just with Israeli ingenuity and necessity, but large amounts of direct funding from the U.S. DoD.

Or perhaps it's the massive infusion of funding that makes the US defense industry breathtakingly inefficient? :-)

The US defense industry is breathtakingly efficient at extracting money from the US government, which is, after all, its whole point.

The US military procurement system may be breathtakingly inefficient at procuring cost-effective equipment, but that's a different issue.