In regards to your last comment, it has been shown many times over since testing began that pitchers have been doping as much or more than hitters, so higher K totals, which are often tied to more velocity, would be expected during the height of an era of doping. Regarding the changing times, I think you look at the construction of the bullpen as much as the limits on the starter in the modern game. If Justin Verlander loads the bases in the 8th inning after 122 pitches, he's likely coming out for a specialist to get the batter at the plate to attempt to ground into a double play, who will then be followed by a specialist for the next hitter to combat handedness. Then the 9th will bring the closer, and game over. In the 1940s and 1950s, you had a pitching staff of 7-8 on a number of teams.