Certain countries, like Russia and Venezuela, are under economic sanctions over actions the so-called World Community deem to be crimes, such as Russia's take-over of Crimea. Such countries would of course be looking for ways to escape the sanctions so they can act freely. According to an NY Times report, both Russia and Venezuela are looking at creating government-backed cryptocurrencies that can be used for international financial transactions outside the normal financial system. They're clearly not planning to adopt an existing cryptocurrency, but to set up government-controlled currencies that just happen to operate over the Internet and use cryptographic controls.
Cryptocurrency (Bitcoin, Ethereum, etc) proponents have been pursuing a libertarian-paradise dream of a completely open currency outside government control that is safer than so-called fiat currencies. Regular currencies have designed-in periodic economic crashes, built into the core design of the currencies, and cryptocurrencies are free from such problems. But ... will Governments allow such activities to become significant and take over the actual economy? Most likely not, and the most likely result is for Big Corporate and Big Government institutions to adopt blockchain/cryptocurrency technologies while outlawing the existing currencies.