If there is a system, it can be manipulate and exploit. Nothing can be regulated for long. Governments are trying to control cryptocurrencis because they are becoming aware of the danger which can snatch absolute power from them. This power is money on which governments had monopoly and full control. But cryptos are decentralized which is against the will of these governments. That is why they are trying to exploit any loophole which may provide opportunity for them to control this market and attack any effort that may challenge their authority.