The F-106 actually proved that the need for such aircraft was simply overstated.
Here's What You Need To Remember: The F-106 Delta Dart proved to be the last dedicated Air Force interceptor, and the aircraft were gradually retired by the early 1980s. Some of those aircraft were converted into target drones and designated QF-106A, while six were retained by NASA for test purposes and used throughout the 1990s.
Throughout the Cold War, the United States Air Force continued to develop interceptor aircraft to address the threat from Soviet bombers. This included such aircraft as the Convair F-102 and the North American F-108, and finally, the Convair F-106 Delta Dart, which was designed to be the “Ultimate Interceptor.” But in the end, the F-106 actually proved that the need for such aircraft was simply overstated.