That question could be reversed.
Why is it that a 15 mile ET spacecraft is automatically interpreted as a photographic flaw or digital artifact?
While I agree that most "ufo" cases can be resolved with conventional explanations, some can not (such as the 1952 D.C. flyovers, this photograph, and others). While this may in fact be distortion of some kind, to just automatically assume it is and forget about it isn't the right way to go.
O'Neill's cylinders would've been up to 20 miles long and 4 miles across.
