[bones6]

If gesturing is a more effective way of speaking, then it make sense for the power structure to take it away from the subordinates. If a private could convince his superior to believe something or do something then it upsets the hierarchy. Maybe there's unscientific words like hypnosis or mesmerization you could attach to this idea of gesturing with speaking.

In D&D, there's somatic, verbal, and material components to spell casting. Somatic components are the precise hand movements to aid in spell casting. That fictional idea/meme had to have been generated by some real-world phenomena, no?

Edit to expand: I also think this may be why even beyond the military there seems to be a widespread stigma against gesturing while speaking. Not that a majority of people look down on it, but that some significant percentage tend to do so at least.

It might seem unfair to some parties to have these extra gestures "used" on them to convince them of things that go beyond what the words they use actually mean. I know personally, I much much prefer to read what politicians said, via a transcript, rather than watch them speak. Their body language + gestures + tones can really change perceptions so significantly that I don't want to let myself be preventably persuaded by otherwise disagreeable positions.

[aksss]

I think it’s far, far simpler than that, and no conspiracy about power is required: moving hands attract the eye of enemies, pointing and mimicking movement give away elements of what’s being said. Hand signs require visual contact with those being addressed. If you’re behind me and I ask you “where” and you say “over there” and point, what good does that do unless I turn around, take eyes off what I’m doing and ask you to repeat. There’s more overhead involved in communicating that way. I think these are some very practical reasons for it. I also think the advantages of using hands in explaining something (to clarify) may imply that your words alone are not clear enough. It’s an important skill to be able to speak clearly and succinctly in times of collective stress.

[bones6]

Very fair and thoughtful counterpoint. I think I may have been imagining that 'smart aleck private trying to get one over on the brute drill sergeant' trope.

Totally agree that tactical communication requires brevity and clarity.

[prashantsengar]

Your idea of reading a politician's speech's transcript is really good. I will do this too. Thanks for this valuable idea.