I was drawn to this by mention of crank length. While 175mm cranks may fit the mythical average rider perfectly, as someone with significantly-longer-than-average legs, they don’t fit me. I wonder what the population’s average leg length is?
Average leg length is about 32 ish inches for an average ish bloke of about 5 foot 10 ish (Europe).
175mm cranks are also about the maximum length for someone with average legs. (They were too long for me. Despite being pretty average.)
Leg length isn’t that tightly linked to Crank Length though, it’s more about Hip, Knee and Ankle flexibility with a side order of leg length. Those with long legs can use longer cranks, but quite a small limitation from “perfect” flexibility will the crank length you need come down a lot.
(This is all based around pedally things, not gravity stuff.)