Putting aside that modern plane autopilots can also navigate and land planes, the common definition of words is often more important than the technical definiti

Putting aside that modern plane autopilots can also navigate and land planes, the common definition of words is often more important than the technical definition. Especially when it comes to marketing to the general public. Terminology gets reused because it has a common usage and somebody wants to use that to frame their new & shiny product. Ask a normal person what they think autopilot does and they'll say "the plane flys by itself". Using that for cars becomes "the car drives itself". Same for copilot, most people probably think they're there to help the pilot.