Some bare aluminum aircraft do have a pretty good shine. In peacetime I saw many squadron or wing commander's aircraft that are kept quite shiny. Many civilian aircraft have owners who keep them pretty pristine.
And airliners in the forties and fifties put a lot of effort into shining their aircraft. Later, with the inflation of labor costs and increased size of aircraft they had to give that up, and went to painting or conversion coatings.
Also, prototypes in the thirties were really shined up. A polished BMF was considered an indication of company image, and a mirror-like finish was quite common on these planes.