Seems like it could be a carryover from a feudal system that ramped up as nationalization happened during wars (WW1 mobilization for example). Modeling of “duty” was for a specific cause.

Duty is for soldiers, servants, employees, and in a smaller way citizens (to pay taxes) in a free society. Now, if you ask people hey would you like to support the less economically well off in society, in theory people can vote on that as being a “duty” of government or a civil service, like a conservation corps.