Possibly because the images come out with a white border, "à la Polaroid", even though the printer doesn't set the machine for the border?
That also require a certain precision in aligning the white stripes with the actual frame made by the camera. A recipe for problem (supposing that for somebody using a Diana a problem really is a problem).
who cares if it is square format or rectangular
more people buy film its a good thing.
i like my pentax, i won't be buying the diana,
but it looks nice.