Just a few thoughts from an Audible addict - not sure if this is of interest.
I can't read a physical book these days because of issues with my eyes. But I have to always have a book going, so 7 days a week I have headphones on and Audible playing… on days when my wife is working I might listen for 6-7 hours.
In my experience, 'said' can become incredibly obtrusive and invasive of the reading experience. There's been a book where it was so bad that I had to quit listening (my memory is terrible, and I cannot think of its title). And in a fair few other books, passages where it seemed every other word was 'said'.
This might happen with a bit such as this (made up dialogue):
Mary said, "What's that to me?"
Harry said, "So, you just don't care?"
"No," she said.
"Well, why should I care then," he said.
"Good for you," Mary said. "You've gotten there."
Part of it, IMO, is bad writing… just using the one dialogue tag, not giving the reader credit for following the speakers by the context of what's being said (which could allow dialogue tags to be omitted). And with bad writing, a wall of saids can seem to be built that stops your forward progress in a story.
But HB is right, too… it can just be the emphasis of the reader. A good reader puts the emotional emphasis in dialogue on the words that are being spoken (giving life to the characters), and the dialogue tags can feel almost an aside, an addendum to a passage that doesn't draw attention. There is a subtle de-emphasis in the speaking, say, of 'he said' (and then the tags disappear).
But when a mediocre narrator is paired with bad writing, 'said' can be so d*mn annoying.
My guess would be that authors who write primarily for Audible (and there are many, I think) are aware of such issues as the way dialogue tags are perceived, and shape their writings to avoid such problems.
Just my thoughts. Interesting thread, CC