Eh. MLB is going to transition and adopt full ABS on every call in a few years. Said this the other day. Tennis first implemented hawkeye as a challenge system. It started I believe mid 2000's on hard courts. Now the tech is used on grass, clay, etc.
The beginning of this decade, big tournaments started eliminating line judges and just went full hawkeye for every shot now. And now pretty much every major televised tennis tournament owrth a damn, has eliminated line judges and uses hawkeye. Clay tournaments don't because the ball leaves a mark on the dirt and the traditionalists still want that.
But in MLB the umpires are much more scrutinized. In tennis the chair umpire could overrule a line judge's call without a player challenging, In MLB the home plate umpire can't overrule himself.
In a few years the balls and strikes will be called automatically and fed in to the home plate umpire's ear via headset and they'll just do the hand gestures for show.
MLB just wants the umps to get scrutinized so it will be easier for them to do full ABS (and still have umpires, just not for balls and strikes). Public will accept it in a few years.