I know it's been a while, but, a couple things...
#1: No, managers basically cannot argue balls and strikes anymore. Those that do are immediately thrown out of the game. That's an unwritten rule in the umpire book now.
#2: Baseball management is NOT a formality, and goes way beyond pitching changes. Lineups and pinch hitting matchups, throwovers to first, steal attempts, bunts, hit-and-runs, even individual
pitches
in late innings... all called from the bench. These calls are relayed to the base coaches in offensive innings, or the catcher in defensive innings. It's quite similar to a head coach in football that calls plays.
#3: I don't disagree with you, I do love a good manager tantrum.
That is all.