At a time where I see currencies moving away from cash to digital I think the reason is partly so that governments can control the flow of their currency more particularly for laundering. They can possibly gain more taxation from a cashless currency because cash cannot be fully traced. If i sell my car for cash to another individual the government dont get any revenue from that because it is not traceable.
So in a governments aim to control our money it will leave a big opening for bitcoin and other decentralised crypto to exist along with fiat and will allow people to "trade" anonymously with each other over a completely independent infrastructure.
Governments are trying to get more control and citizens are realizing that governments are crossing a line and that they are going too far with their desire to control things that is why I think bitcoin is going to become successful because people are going to realize that is a future in which they do not want to live.
of course with the advantages possessed will make the payment tool option for the future. and I think government is just not ready to face change, but later will follow it too