As far as I know, from the FD to te EOS mount canon never had a pancake lenses while nikon and pentax always had. Now all knew that canon bodies always had small flange distance making it the most adaptable for other make lenses. Can it be for this small distance be the obstacle for designing a pancake?
Long ago, while on a trip to Tokyo, I saw an interview with the CEO of Canon on the TV. This was around the year 2003 or so. It was a very long interview, in Japanese, but I was able to watch it with a colleague of mine. Most of it was pretty staid stuff, but at one point the CEO was asked if Canon would produce a pancake lens. The CEO became visibly agitated and responded with a tremendous, emphatic NO! There will NEVER, EVER be a pancake lens with the Canon name on it. NEVER!! He was clearly disturbed at the idea of a pancake lens. I could never really understand why because the translation could not keep up with the TV feed and the interviewer quickly moved onto something less controversial after upsetting the CEO so much.
I guess there has been a change of leadership since then.