They can work against ballistic missiles, which is why the attackers used drones & cruise.
I assure you that low-level defenses are on their way, or arriving now.
The Saudis produce 10% of the world’s oil. The US has an interest in seeing that continues. In fact, the Gulf States produce 20+% of the world’s oil.
Take that oil off the market and gas is over $6/gal in Houston. Our exports of everything are down 30% and our allies are nearly off the air.