I don’t think they deal in absolutes, they’re just making decisions in a given situation where the numbers dictate they should do something, and truthfully, the only alternative is the managers gut feeling. And let’s not pretend that the aces and a lot of #2s in baseball are still given lots of leeway in when they are taken out. It’s usually the mid and backend guys that get yanked earlier because they already have a larger degree of drop off in results as the game wears on.
I think the real issue here is that people have rosy memories about “that guy” who gutted out that one start even though he was getting hit around, never gave up a run and went as far as he could before the pen took over with the bases loaded and that guy came in and put out the fire. It was tense, gut wrenching, so emotional. Emotional memories are far more powerful than the ones that aren’t accompanied by that. That’s why fans in general don’t like blowout playoff games in any sport, they like low scoring tense games because they form more vivid and emotional memories.