Defense is about layers of protection. Killing a missile in boost phase is obviously ideal, but that's not always possible, so other forms of vehicle kill are necessary to explore. Patriot systems are terminal phase defenses, as are CIWS (on smaller missiles, much closer in), and then there's THAAD.

The fact is no one system can protect everything against every method of intrusion. We have security focused on finding those shipping containers, and other defenses against other threats. Its all about a total picture.