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.
That's what I have said before, even bitcoin is decentralized and absolutely peer to peer in every transaction there is a big possibility that government gain a complete taxes from bitcoin transaction if there is a new additional features created for that kind of matters in terms of generating income to government.