The most aero position on a road bike is on the hoods with the forearms bent horizontal. Sure, you can have this position on a flat bar hybrid, even with bar ends, but this is not a position that is easy to hold for long period of time, especially for riders whose fitness and core strength is lacking. A slightly less aero but easier position to hold is on the drops with slightly bent arms and head up. Both positions are more aero than just being on the hoods with slightly bent elbows.
Having drops offers the option of alternating between the two most aero positions. That is the real advantage of having drop bars.
From my own personal experience, riding my converted Rapid is much more enjoyable than the old Rapid. But I've also upgraded it to better components and drive train, so that has something to do with it.