The A-Team: Why Is MLB Waiting To Implement Automatic Strike-Ball Calls?

This coming spring training, Major League Baseball is going to have the same automatic strike/ball calls, that allow for instant replay to possibly correct the call on the field. This conversation between Adam Clanton and Adam Wexler on The A-Team; stems from the fact that MLB Commissioner Rob Manfred is going to meet with media in Arizona next week. The conversation centers around, why is this not already in use for baseball's highest level of play?!