Do you know what separates a black market from a regular one? Do you know what separates crypto currencies from fiat currency? Believe me, countries like the US and China are finding any chance they can get to take advantage of crypto currencies. They're losing tax money, and tracking crime (such as drug deals) is made so much more difficult, so it is very much within their interest to regulate it. If it were so easily done, it would have been years ago.