A majority of "everything you could possibly want to buy" includes physical goods and physical services.
Markets cannot be completely decoupled from states as long as they trade in real goods and services - as long as you're not trading solely in virtual goods, the other part of the transaction still requires you to interact with the real world under the jurisdiction of some state, and thus the whole transaction, including the cryptocurrency (and the source of that cryptocurrency) is subject to those rules.
If you sell some virtual services for cryptocurrency and later want to buy a car with the proceeds, then not only the car purchase, but also your sale of these virtual services must have been done "cooperating" with all the rules of fiat - states can and will forbid using the proceeds made in markets completely decoupled from their systems of financial regulation; they will use their hold over the physical markets to try and regulate the virtual markets also as much as possible. In the long run, if cryptocurrencies won't cooperate, then they'll be ostracized - there's nothing stopping the gov't from passing a law that simply prohibits any legitimate merchant to accept bitcoin, greatly limiting the range of things that you can actually buy.
Markets cannot be completely decoupled from states as long as they trade in real goods and services - as long as you're not trading solely in virtual goods, the other part of the transaction still requires you to interact with the real world under the jurisdiction of some state, and thus the whole transaction, including the cryptocurrency (and the source of that cryptocurrency) is subject to those rules.
If you sell some virtual services for cryptocurrency and later want to buy a car with the proceeds, then not only the car purchase, but also your sale of these virtual services must have been done "cooperating" with all the rules of fiat - states can and will forbid using the proceeds made in markets completely decoupled from their systems of financial regulation; they will use their hold over the physical markets to try and regulate the virtual markets also as much as possible. In the long run, if cryptocurrencies won't cooperate, then they'll be ostracized - there's nothing stopping the gov't from passing a law that simply prohibits any legitimate merchant to accept bitcoin, greatly limiting the range of things that you can actually buy.