Interesting reading comments here. I spent many decades on my old Super Sport and it slipped my mind what length the Ashtabula cranks were. I measured and they were 6.75”. Hmmm, that comes out to 171 mm. Several of the early Sugino cranks also came in 171 too I think. We’re they just going with what we Americans used a lot of?
As an aside, I got a woman’s parts bike that came with some 165mm cranks that I may try sometime. I’m about 5’10” with a shorter inseam, so might be fun.