Sure, a government cannot easily prevent its citizens from issuing transactions. But why should it?
Typically the goals of a government will be to prevent its citizens from bringing certain items into the country (like drugs or weapons), take other items out (like national heritage artifacts, gold, diamonds), being bribed or financed by foreign corporations or governments, and giving the national currency to foreigners.
Sure, each government would like to keep the monopoly for their own profit; makes perfect sense!
The first two are physical border and mail policing problems that do not depend on how the item was paid. (Importers of illegal items are generally nabbed when they receive or try to colelct them.)
The other two uses are partially caught when the citizen tries to spend the bitcoins locally, or convert them to cash. So they can be curbed by closing local bitcoin exchanges or imposing strict AML/KYC measures on them, control of bank accounts, banning bitcoin from e-commerce and large property sales (vehicles, real estate, etc.) Which is pretty much what China did.
Well; not really. China just made a couple of moves that seriously disrupted the BTC price (but at the same time, no one can say for sure if their acts were the actual reason). The incentive could be a whole lot different though... I guess we will know within the next decade if you're right or not.
The only remaining use of bitcoins that a government may be unhappy about is corrupt officials and subversives being paid in bitcoin but saving them until a later time, when they leave the country. But, in that case, a bitcoin bribe is no different than a dollar bribe deposited in a foreign bank, in the guy's name.
Bitcoin is often claimed to be a way to take one's wealth out of a county, bypassing the government's currency controls. But while it works for the individual, its effect on the country's economy is quite different from the usual ways of "taking one's wealth out".
Unhappy? I beg your pardon Jorge; this is how the governmental machine rolls! Bitcoin / Moneroj / Fiat / Diamonds or PM, the spice should always flow. Or else!
The usual ways are taking valuable propery (gold, antiquities,etc.) out, and/or selling local property (cars, real estate) for foreign currency to buyers abroad, and/or exchanging the national currency for some foreign currency, either before or after moving out. The the currency exchange route ends placing some of the national currency in the hands of foreigners. Either way the country gets poorer, which is why governments often try to limit such transactions.
The situation is different when the citizen uses bitcoin to "take his wealth out". If he already had bitcoins, it is like him having euros or dollars in a bank account in Switzerland; the money was already out of the country to begin with. If he exchanges his local currency and/or concrete wealth for bitcoins in the local market, these items will pass to other citizens: the country will not get poorer, and the average citizen will get slightly richer. (It is the Americans who will become slightly poorer when he moves to the US and starts spending his bitcoins.)
This sounds like a plan; funny that almost the same thing has been proposed by Yianis Varoufakis as an antidote to the Greek economic disease - in the midst of his contradictory beliefs about "the usage of BTC as a currency is a totally flawed idea" to begin with. Nevertheless; there's a funny coincidence here, which I don't find particularly random...
