As I understand it, in baseball, some subset of the calls made by an umpire are open for review, at the request of one of the team's managers. In those cases, the managers are allowed to leave the dugout and question the correctness of the call. At that point, they can ask the umpire to either officially review the call (which each team has a set number of), or the umpire may decide to voluntarily review it under their own discretion.
However, "judgement" calls by an umpire, such as balls and strikes calls, are not review-able. A player or manager arguing with an umpire over such calls can quickly lead to an ejection.
I can understand e.g. a player at the plate, in the heat of the moment, mouthing off to the plate umpire when they disagree, but for a manager to come out of the dugout and argue knowing they're going to get ejected seems odd. Frequently I will even hear the commentary team speculate that being ejected was the intent of the manager.
So, why do managers argue over these calls when it's always fruitless? Is it always fruitless (e.g. do umpires ever reverse ball/strike calls)? Or is there some reason a manager would want to be ejected from a game?