What a big fucking surprise. A lot of people involved in the decision making probably doesn't understand how it works anyway. Moving along.
I'm sure they understand it perfectly. But if cryptocurrency becomes the norm, they lose all control.
Currently they have the power to influence interest rates and adjust the printing of USD to control the inflation in the US. Through this they can post-pone inflation or a recession. This can be played in their advantage in international affairs as well as domestic and if they standardize Cryptocurrency they lose their most powerful weapon, the economy.