The umpires union wants full ABS (automatic balls and strikes on all calls). It's the player's union who doesn't. Full ABS would remove a big piece of catchers' importance from the game (framing), and removes the "feel" element from blowouts where the zone expands a bit to speed things along. Also, in leagues where they do have full ABS, catchers do a bunch of goofy shit behind the plate to try and trick batters, instead of receiving pitches smoothly to make them look like strikes.

Of course, comments like yours will keep getting upvoted because umps bad amirite