I don't think banking system is worried at all about the emergence of cryptocurrencies. Because their lobby is super strong and has been deeply rooted within society since hundreds of years. A mare cryptocurrency that emerged just 11 years ago, can't destabilize the foundation that banking system has built around the world.
It is true that the banking system has been deeply rooted in the society for hundreds of years, yet they see Crypto currency as treat to their system, some fight to erase it from the surface of trading and payment because it is like nothing they have seen but unfortunately it has grown more than their power can do. If you truly take a good survey you will discover crypto has gain so much energy and adoption that the banking system is becoming uncomfortable and starting to worry
They do not see it as a "threat" per se, because they can use it just like you and me. It could be decentralized and maybe they won't have the chance to have a power over it like they have power over fiat, they can't be bailed out neither because nobody can print more bitcoins to help them out, all of these are bad for banks and I understand why they would want something better suited for them.
However one thing is true, if you can make money from bitcoin, so they can, there is nothing stopping a bank to buy a billion dollars worth of bitcoin, which is why I think they are not worried all that much. Obviously they wouldn't prefer this, but they do not see it as a threat neither, they see this more like a inconvenience to their already working system to make them richer.