I've often wondered why this enthralling scene was only told by the junior Hobbits. Was it to strengthen their characters, or was it a throwback to the old way of storytelling, in which everything was told in the third person?
I think it was told by the junior hobbits because they had the direct connections to Aragorn, Gimli, and Legolas.
It is very funny and rather dramatic not to know what happens... and then have Merry and Pippen at the door (smoking and sleeping)... It strengthens the love between the character and elevates the characters above the action.
Maybe Tolkien wasn't satisfied with his writing of the "action"... couldn't do it justice, etc., so reverted to narration. (That's what I'd do, but I'm no genius and he writes everything so well).