Force mostly has to be individually applied, and you can only take it so far before you have massive pushback in the form of civil unrest.
Printing money, to pick a simple example, is much more effective and can be done across the economy as a whole.
Could you imagine police forces breaking into everyone's home and taking half their cash in a matter of days? It's unthinkable that that would happen for logistical reasons alone.
But that's what we've effectively seen some modern western governments do just recently by rapidly deflating their currencies.
Abolishing fiat currency would take away that power, and make no mistake it is an immense power. It's the power to shape entire economies at the stroke of a pen.