Originally Posted by
timtak
why bikes went from being very aerodynamic in terms of the rider bike combination in the late 20 century, to having very aero frames but tall headsets, and UN aerodynamic ride-bike combinations (unless a lowering stem is used) in the past two decades.
For the vast majority of riders, I think this is a false premise. Even among slim and fit roadies, most choose fits that don't involve flipping and slamming the front-end fit to its limits. And if they're not doing that, if their fit isn't bottlenecked by that stack, then it's not obvious why a lower stack would motivate use of a lower bar position.