Because bitcoin can not be controlled, the government can not control bitcoin, worrying that bitcoin can undermine the economy. And bitcoin is anonymous, Bitcoin is exploited by criminals and the government can not track it.
that is not the reason, actually bitcoin can help the economy of any one's country, it helps every nation to grow unimaginably. some government officials in other countries banned bitcoin because they are just scared because in the future, they know that it will not be controlled by anyone due to its demand. I guess,Some government's impression about bitcoin is that it's heavily used in money laundering and crimes that's why they ban it. this is every government is own right.i feel that,today and tomorrow it will be legal .
indeed, bitcoin is used in crimes by sending funds anonymously. we all know that, but its all about the people who used it. we are all hoping that bitcoin become legal around the world. i want to experience the feeling of buying everything i want by the use of bitcoin.Because if they allowed it, other banks may have been ignore or others if allowed bitcoin some people used this in bad things. But the main cause for me to what government ban bitcoin is to they get no interest from the people who earn bitcoin in other words they got no money .
you mean by collecting tax to the people who use bitcoin and earn money through it? actually that is one of the main advantage of bitcoin, since it is untraceable of whoever send and receives it no one will know who they collect the tax with. that is also why they dont want to support it. 