It's got nuffin to do with aero. You could get 'flat' bars as low as your drops if you really worked at it...they're called pursuit bars generally.
It's about choice. A truly aero position is not sustainable for long periods of time, by anyone no matter how fit. That's why even the pros spin along on the hoods generally.
If your bar doesn't give you any choice, you're locked into a single compromised position, or two at best (bar ends). Many folks don't care about that, and that's fine. That doesn't make it any less of a disadvantage though. Some guys tour with those crazy 'butterfly' or 'trekking' bars, they probably work great. It's all about flexibility of choice.