Just because a big drop works for some -- tall or short -- doesn't mean it works for everyone (comfort or efficiency-wise). I'm 6'1". If I lower my bar from 4cm below saddle to 4.5cm, my power drops 20%+. No discomfort issues until I go a lot lower (mainly in the neck), but given I live and ride in the mountains, I'm MUCH more interested in efficiency than in trying to get aero, even if it were a bit more comfortable.