Unless you're in a military unit that is on the march, what does the number of steps in a kilometer matter for at all? And there is a huge natural variation in human stride length anyway -- you won't be surprised to know that the figure you mentioned for miles is an average that only applies for adult males of military height (i.e. not even shorter men). I think SI units are great for measuring distance at scale. Nanometers, micrometers, millimeters, centimeters, meters, and kilometers are all in common usage, and can represent pretty much anything you'd need. By contrast, it's imperial that has the real problems with use at scale, specifically down at tiny scales.