The governments dont want you to use bitcoin as they cant controll it... for example if you have a bank account they can freeze it and stop you from recieving and sending money with bitcoin you cant do this as bitcoin is decentralized and nobody has controll over it. This gives people unlimited possibilities to launder money and do other things which are illegal BUT on the other hand is gives you the maximum controll of your wealth and this is not something the governments want for you...