Cryptocurrency is decentralized thus it becomes absolutely difficult for many countries to regulate it therefore there isn't any other option than to ban it by those country, the fact that some wicked people adopted cryptocurrency for money laundering for terrorist is another setback for adoption of cryptocurrency in majority of countries who had banned cryptocurrency though even before cryptos a lot of money laundering took place however it becomes imperative for most countries to checkmate and monitor all financial transactions involving crypto which is most often very difficult to track thus it was tagged as illegal.