I Navigated Navy P-2s and P-3s for 20 years. The P-8 also has a flight navigator/radioman. The civilian equivalent disappeared several decades ago, replaced by automation.
The story about how Boeing convinced the FAA to certify the 767 and 777 cockpit configuration (pilot and copilot only) is an interesting one. On the flight-safety test, Boeing had a 777 take off, fly a prescribed route, and land with *nobody* in the cockpit. That convinced the FAA that a flight navigator was not necessary in the cockpit of those aircraft.