is not that bitcoin able to change the state of its users which effects also on the state of the country's economy, why even banned hemzzz 
Maybe because it is highly encrypted and highly confidential with regards to identity that whatever happens, there is no other way or reason to investigate since there is no information to use for during investigation. Secondly, it is not yet legalize in some other countries because it takes so much time, money and effort before it happens and there are so many things to consider with.