It's always been my understanding that the drops are supposed to be the same height has the flats on a standard MTB. Most of what I see here have the drops below the top tube, road bike style.
Modern Brifters are designed such that your primary hand position is on the hoods. It only makes sense that the bike should be configured around your primary hand position. The drops are predominantly used for short term while descending. Reaching for the brakes is not the most ergonomic undertaking in the drops, but the trade off is much improved aerodynamics, control, and the full leverage afforded from the grasping the long end of the brake lever. The tops are generally used for sitting upright for a rest or navigation, or other recreational, non-standard events.