What it gets down to is the natural evolution in all team sports at the elite level towards specialization. Usually professional sports leagues eventually embrace specialization, and the skill level of the sport is higher.
We could go back to two-way players in football, but guys would not be quite as skilled in some areas and would need to pace themselves more. The “no greater than 100 pitches” pitcher is similar. The game of baseball at the elite level today is broken down into sections, where you have one pitcher cover the early innings, and others for the middle and late innings. Specialization.
Now there is talk of this silly “golden at bat”. Lets hope we never go that far from the original rules.