Non Radar is taught because outside of the [vfr] tower it is the foundation of separating aircraft. Long before there was radar, there was non radar separation. Radar was implemented in the en route environment after two planes collided. Why did they collide at the same altitude, because pilot decided to lie about his reported altitude to show people the Grand Canyon. Radar was first used at busy terminal facilities.
Non radar also teaches you the fundamentals of coordination with other controllers.
Once again, non radar is the foundation of active separation.
Air Traffic Control (as opposed to air DEFENSE) RADAR was used in WWII England to guide landing aircraft safely, amongst other control/defensive uses. Ground Controlled Approach (GCA) was used to guide landing aircraft to a safe point where the pilot could see to land. Yes, in some unsual circumstances, the aircraft was guided down to touch-down. The early USAAF GCA units were the AN/MPN-1. Google for more info/photos.... ... ... Radar was first used at busy terminal facilities. ... ... ...