One thing that I have never understood is the huge combined shifter and brake conbination. They are actually huge and heavy. They also put more shift cable out in the wind.
In the middle to late 80s we had the down tube shifters. They were out of the slip stream and had very little drag from internal drag in cabling. All they had was the under BB guide and the turnaround at the rear derailer. With so little in the way of cabling and guides the derailer adjustment almost never needed attention. Besides that the the shifter levers were quite light. The bottom line was to make the bike much cleaner lighter and less cluttered. The reach down to the levers was no big deal to racers as they are all hunched over anyway.