Why did the E-2 Hawkeye not adopt external drop tanks?
Short answerIts existing endurance and access to aerial refueling met the mission, so external tanks offered little operational need.
NotesThe E-2 Hawkeye already has sufficient endurance for its normal carrier-based airborne-early-warning orbit. It does not routinely operate so far forward that external tanks become essential to the mission. Aerial refueling can cover the relatively rare cases that require more time or distance. The answer treats extra tanks as a solution to a requirement the aircraft did not have.