Compared with the present, professional baseball in the early 20th century was lower-scoring, and pitchers, including stars Walter Johnson and Christy Mathewson , were more dominant. The " inside game ", which demanded that players "scratch for runs", was played much more aggressively than it is today: the brilliant and often violent Ty Cobb epitomized this style.  The so-called dead-ball era ended in the early 1920s with several changes in rule and circumstance that were advantageous to hitters. Strict new regulations governing the ball's size, shape and composition, along with a new rule officially banning the spitball and other pitches that depended on the ball being treated or roughed-up with foreign substances, followed the death of Ray Chapman after a pitch struck him in the head in August 1920. Coupled with superior materials available after World War I, this resulted in a ball that traveled farther when hit. The construction of additional seating to accommodate the rising popularity of the game often had the effect of reducing the distance to the outfield fences, making home runs more common.  The rise of the legendary player Babe Ruth , the first great power hitter of the new era, helped permanently alter the nature of the game. The club with which Ruth set most of his slugging records, the New York Yankees , built a reputation as the majors' premier team.  In the late 1920s and early 1930s, St. Louis Cardinals general manager Branch Rickey invested in several minor league clubs and developed the first modern " farm system ".  A new Negro National League was organized in 1933; four years later, it was joined by the Negro American League . The first elections to the National Baseball Hall of Fame took place in 1936. In 1939 Little League Baseball was founded in Pennsylvania. By the late 1940s, it was the organizing body for children's baseball leagues across the United States. 
But rule isn’t in place to stop practical jokers. What ultimately did the tradition in was how unsafe it is to have a foreign object on the baseball field, and how likely it was for an idly-lying glove to change the outcome of a game. You can pretty easily imagine a player trying to line up under a popup and instead tumbling over the opposing shortstop’s glove; that can lead to an injury and an error, both of which are best avoided. While the rule was a bit controversial when enacted — like many other rule changes, tradition weighed heavy — it gained acceptance shortly thereafter, and today, is taken for granted.