bitcoin has no central government so any of gov department cant track the transaction so some of the contry still bann for the bitcoin use 
It is used on some illegal activities and the Government do not know anything about it because they cant track the transactions of Bitcoin. Although some country still accept bitcoin without thinking this.
If you think of it, Bitcoin really favor the users, than the Government. Bitcoin is free and you can really do anything with it, that is freedom for you, though that is the reason why some government are minimizing the use of these digital currencies.