The cruise ship St. Louis glides steadily and serenely past the camera, while passengers on deck wave handkerchiefs at the camera..... and by extension, the audience.
That's the sort of immediacy that motion pictures offered that still photography could not: that motion gave the audience the sense that they were present. A still photo was more accurate that a painting, but just as dead. By making use of the superior clarity of British Biograph's 68mm stock, the audience becomes more fully invested in the movement. And the moment.