Why do you think Stevenson chose to tell the story from Utterson's point of view rather than using Jekyll and Hyde from the beginning? How does...

Stevenson likely chose to have Utterson narrate the story so that the audience would see the story unfold as he does, increasing suspense and tension as we must wonder with him what on earth is going on with Dr. Jekyll and Mr. Hyde.  If either Jekyll or Hyde were the narrator, there would be almost no suspense because either one would be able to explain to us, from the beginning, what the nature of their relationship is and how they are connected.  However, as it is, whenever Utterson is confused and suspicious, so are we.  Whenever he lacks information, so do we, and so Stevenson succeeds in creating a great deal more suspense by revealing the strange case to us as it is revealed to Utterson.  Then, as he pieces the full story together from Lanyon's narrative as well as Jekyll's letter, we see the big picture at the same time, finally relieving the tension for all of us.