A pitcher comes to the plate 10 times? And they walk even at 20% clip you're taking 4 times a game.
You saved 30 seconds tops.
Maybe in fantasy land, but in reality teams and players are often not prepared instantly for the situation, and the player loaf on an off to the bag to run for the pitcher anyway.
The games take 2 hours plus to play, no way around that at this point. The field is too full of fodder is the isue.