Umpires want to make the right call, but they also don’t want to make the wrong call at the wrong time. Ironically, this prompts them to make bad calls more often.
This argument has also been made for on-air meteorologists erring on the side of predicting severe weather and the reluctance of teachers to give a failing grade.
The biggest problem that I see in these arguments is they imply that these experts are always optimizing towards a single point…accuracy. Instead, I always tell folks that on-air weather personalities optimize towards comfort and safety (edging towards safety). Hitting the precise temperature is less important than the audience not being in danger.
I imagine the same goes for your average umpire. Instead of optimizing towards perfection, I see their role as holding the game together. Keeping arguments from forming and spinning out of control. Calling a ball vs. strike perfectly is less important than respecting the players and the game.
It boils down to the consequences of making a judgement call. When all of the tools available are subjective, with plenty of grey areas, those judgement calls create trust and perceived wisdom.
As precision increases there is a perception that the measurable element also increases in importance. That is rarely true.
Precise tools are best used to support humane/subjective goals, rather than supercede them.