Except crypto isn't currency, it's an artificial resource with no inherent usefulness beyond exchange.
States won't give up their currencies because that would put all of them in the position of, say, Liberia, rather than the position of the US, EU or China who can literally print money to pay.
And even if all state currencies vanished over night, this would change nothing for individuals because the vast majority of wealth is claimed by a minority of individuals and the only thing guaranteeing their claim is the exact monopoly of violence of the state that also backs its currency.
You don't have a private yacht because the state guarantees the value of your money with violence against foreign nation state actors. You have a private yacht because the state will ruthlessly punish anyone other than itself trying to take it away from you.
The state may be holding a gun to your head to be able to take away what's yours at any time, but it also holds a gun to everyone else's head to prevent them from taking it first. This is why the extremely rich spend so much time, money and energy influencing politics. Not because they want to dismantle the state, but because they want to keep it from using the gun against them while still keeping it pointed at everyone else.
Without a state threatening violence to protect your claims on "private property" you'd literally have to raise your own private army to defend it. This is why leftists call anarcho-capitalism "feudalism with extra steps".