I think the governments do not want the BTC to affect their economies. I think because they have not seen the real value that Bitcoin can bring to the economy of their country.
We all know that we can't please everyone to believe in what we believe because everyone has its own free will, I'm just hoping that in the future majority of the governments in the world will see the potential of crypto currencies and make it legal on their respective countries. It's true that there are some governments that see Bitcoin or crypto currencies as a threat to their economy and a threat to their citizens, maybe they have a different point of view and we just need to respect them. 
Each country has a different policy, in some countries bitcoin is legalized but there are also those that prohibit the use of bitcoin in their country. The goal is to protect its citizens from the bad side of bitcoin. As a bitcoin digital currency is clearly not wrong, the wrong is people who see a gap to misuse the system in bitcoin trading and cheat or do illegal business. That is what the government feared.
That's correct, and the misusing of this technology is one of the reasons why other governments ban or prohibit their citizens to use or possess this kind of digital currency. In my own opinion and point of view, it is better to regulate and amend the use of Bitcoin or other forms of crypto currencies because this technology has a very huge potential and governments already saw that but making legislation takes a lot of time especially when it is not prioritized by a specific government. 