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.