They are creating vehicles that take tiny numbers of people into space at mind boggling expense (it was $10,000/lb but I don’t know now). The engineering of such things requires parameters; it’s not optional. And it makes no sense to build for the extremes; the vast majority of humans are in a small size range. The cost to build for the people at the ends of the Bell curve would be exorbitant. So they engineer for the 90%.