In the beginning, machining was less complicated, at least it seems that way from present day point of view. Material available for use was found on a much shorter list. Options for machinery and tooling were more limited. Coolants and lubricants were literally water and oil.
Today, we are presented with nearly unlimited options in the machining process. Tooling has improved, so have available coolants and lubricants. Engineers and designers are willing to stretch the limits of what is possible. Manufacturing is left to produce a part that matches the specifications of the print. A