You do realize that even back in the 1870s, it took time for the batting and fielding teams to switch roles? Until the 1954 season, players left their gloves on the field (obviously after they began using them)--1B/3B in foul territory, OFs by their position, C/P on the dugout roof, middle infielders on the infield grass just off the dirt. Of course, pranks were played: missing gloves, content added, and if I recall correctly from games I watched in the '50s, infielders began bringing their gloves into the dugout and would carry out gloves for people left on base when the sides switched. But they also ran into the dugout and out to the field a bit more speedily than you see today. Say it took a minute to switch sides back when. That adds 17 minutes to a full 9-inning game. In 2018, most games had 2 minutes, 5 seconds for commercial break, which would increase that time by another 18 minutes and 25 seconds. The average full 9-inning game today has about 300 pitches. Knocking 5 seconds off each pitch would reduce games times by 25 minutes. Since they have already started doing some advertising during innings, they probably could figure out how to cut the between inning commercial time but you are now getting into how much the sponsors will be willing to pay in that case. With the players already getting about 54% of the profits, will the owners be happy if their share goes down? And with large, long-term contracts already signed, how will they cut the players' share?