Maybe because base-60 has some numerological property that makes it easier to use than base-72? All I can think of off-hand is that 60/5=12 while you can't div

Maybe because base-60 has some numerological property that makes it easier to use than base-72? All I can think of off-hand is that 60/5=12 while you can't divide 72 evenly by 5. 72 wins at dividing by 8 & 9, but it might be more rare to split a pile of things into that many. 60's divisors connect more neatly back to base-10, but that's probably a modern era concern, not valid back then. Also, your thumb has one fewer exposed joint/pad -- the base sort of blends in with the palm, the final joint is much further down -- so they might have felt it's "different".