One response to the 'hard-liners' on this discussion, and to the situation described in the OP would be "OK. It's your sport, you make the rules, you train the novices, you mark the score sheets"

Within such constraints it's understandable but maybe not an activity for the Joe Offer's of this world.

What doesn't make sense to me is seeking to explain it by reference to generic assumptions about what goes on in different people's heads in heads in different performance situations and with different audience expectations.

From Howard Jones' the presence of a book or prompt, this is only a symptom of a lack of preparation and a lack of confidence resulting in a weak delivery. we have to assume that the situation is very different from a poetry reading . Is it? How so? Can that inform this discussion?

Apart from little Johnny, eyes tight shut, reciting the poem he has just learned by rote to admiring adults how often does someone 'making a presentation' to an audience not have multiple things going on it their head in parallel, only one of which is 'remembering what words come next'. For some people and situations the words that come next can readily be offloaded to a piece of paper to freeeing up processing power for other things.

Many comments seem to describe a grown up version of little Johnny, with some novices regarded as needing the schooling that Johnny's experience from probably part of.