"Benefit" or "Control" or whatever else you want to call it, they are two sides of the same coin. Bottom line is that governments have no say in anything when it comes to bitcoin. For example they can't print more of it or censor transactions. Or in case of US government when they sanction countries left and right they can easily block every fiat transaction but they can never prevent people from using bitcoin. So that doesn't sit right with them that such a simple tool is completely out of their control that has made them powerless.
These tools are not out of their control though. They can still sanction countries and print money all they want because just like how Bitcoin can't be banned and will always be around, so will fiat. And governments know this. Because fiat can act as a last resort mechanism. And Bitcoin can't. So fiat is not going away and governments are not afraid of Bitcoin threatening their tools. Government don't want to buy in because they don't see how it's better than gold for reserves. They don't need to transport their reserves very often and they don't need a censorship resistent currency because they're the ones doing the censoring.