You’re right Stephane, aside from these discussions no-one seems to have any carved in stone reasons for it.
Wheels can be found on just about every type of American safe from the best and heaviest bankers chests of their day, to the smallest “one-man lift” sized domestic safes, and just about everything in between.
They were fitted on the largest Corliss cannonball weighing 33,000 pounds, and yet they were fitted on safes like yours and ones even smaller -I’m as baffled as you! 🙁think):
BTW your little Victor is a beauty- has a different sort of charm you don’t get with our British or European stuff. Good job on turning and ageing the brass finials, agree they will look better shorter, but can still see you done a superb job making them.