I would submit that this approach is due to the old fashioned fixation on seat tube heights. Better, in my opinion, to find a bike with the ideal length top tube, fit the reccommended stem, and not worry about the seat tube size, within reasonable limits. In addition, adjustments must be made for bikes with unusual seat tube angles. Handlebar Height Systems such as the FitKit also make reccommendations for how to adjust the saddle, width and drop of handlebars, shoe cleat adjustment, etc. These systems cannot specify handlebar height because this is not determined so much by the dimensions of the cyclist's body, but by the cyclist's condiditioning and type of cycling activity.
Low handlebars provide a leaning-forward riding position.
Consider two extremes of cycling intensity. Contrast an old geezer who rides 20 miles a year, ambling along at 5 mph on a quiet bike path, versus a racer in a desperate final sprint to the line. The geezer pedals no more than neccessary, coasting as much as possible, expending much less energy than a pedestrian. If such a cyclist is placed on a bike with low handlebars, the weight of the upper body will bear heavily and painfully on the wrists and hands, causing soreness and discomfort to the shoulders and neck as well. This discomfort will quite possibly lead to the abandonment of cycling altogether.