I think they do what they do based on which hand/arm is dominant. If accuracy is important, which is often the case when fishing bass in cover, then you would want to cast with whichever hand provides the best control.
correct - but your dominant more accurate arm is also your strongest one too - not? That's the point of lefthand retrieve baitcaster reels being popular in the midwest - you can fish them like spinning reels always using your dominant arm to both cast and retrieve
only when stamina and all day grinds become key does it make sense to switch back forth between casting and holding during retrieve. That was my theory - but I don't know if it's true or not that bass pros do it that way.
I know all day pitch-fests for walleye with spinning reels can really take a toll on my right arm/shoulder - while my left is fresh comparatively speaking