It's even more simple than that: There's nothing about paper money that enables tax collection either. And yet somehow, taxes continue to exist.
Bitcoin is only a currency, not an entire financial system. It is a replacement for pieces of paper or shiny metal with doodles of George Washington stamped on them. It is not a replacement for banks, or credit cards, most other ephemera that people have constructed on top of currency. In point of fact, people are having to re-invent financial institutions in order to make Bitcoin more useful. And it's those institutions, not the underlying currency, where government attaches taxation.
It may become more feasible in the Bitcoin era to run a financial institution that plays entirely outside the US's jurisdiction. Nonetheless, there would be a large market for legitimized (and taxed) financial institutions, to provide services to the large number of entities that the government would take a hard look at anyways. My gut is that two parallel economies is an unstable situation, and the shadow-economy would not receive must traction compared to the legitimized one.
> My gut is that two parallel economies is an unstable situation
Parallel economies are not only inevitable, they can be long-term stable whenever you can't deal in some (desirable) goods in the legitimate economy. Black markets are very difficult to root out and always have been.
> the shadow-economy would not receive must traction compared to the legitimized one.
Depends on how essential the black market is to getting what people view as the essentials of life. In middle-class First World countries, it's pretty marginal, because most salarymen don't really want heroin that badly. In the 1970s Soviet Union, if you didn't trade on the black market you simply could not get certain goods Americans would regard as utterly mundane, such as bananas. The USSR had a horrible time with black markets and goods disappearing from store shelves and being hoarded in peoples' apartments.
Bitcoin is only a currency, not an entire financial system. It is a replacement for pieces of paper or shiny metal with doodles of George Washington stamped on them. It is not a replacement for banks, or credit cards, most other ephemera that people have constructed on top of currency. In point of fact, people are having to re-invent financial institutions in order to make Bitcoin more useful. And it's those institutions, not the underlying currency, where government attaches taxation.
It may become more feasible in the Bitcoin era to run a financial institution that plays entirely outside the US's jurisdiction. Nonetheless, there would be a large market for legitimized (and taxed) financial institutions, to provide services to the large number of entities that the government would take a hard look at anyways. My gut is that two parallel economies is an unstable situation, and the shadow-economy would not receive must traction compared to the legitimized one.