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.
You can't sell car or house anonymously for cash because it always has to be some agreement done
Cash is going to stay and it has to stay.In my country in EU Europe banks have big problem with his IT infrastructure sometimes during weekends his service is not working and even his cards are not working so it is always good to have some cash
If everything will be digital than it will be very easy to control people
China is punishing merchants what are not accepting cash because it is against law
There is planty of places in my country where i can pay only with cash
In a case of bitcoin cost of transaction is to high and it will be not lower in future
So bitcoin is not internet money