I wouldn't talk in my sleep if I couldn't talk better than that. The actor's manner of speaking has to be free from parsonical sing-song and from all those cadences which lull the spectator so the sense gets lost. People talk for hours without uttering a single topic sentence. Yet we generally understand speech perfectly and instantaneously. We don't have to keep going over the same sentence three times to figure out what the person is trying to say.
People communicate with their bodies much more effectively than they do on paper.
Friends of the critic Desmond MacCarthy, who was a member of the Bloomsbury circle, thought that he was a fantastic talker, and that his genius was never reflected adequately in his writing. One day, some of them invited MacCarthy over and hired a stenographer to hide outside the room and record his conversation. MacCarthy showed up and obliged by talking brilliantly. After he left, the friends waited impatiently for the transcription to arrive. They read it.