The main reason for prohibitions is very simple. Transfers in a currency different from the national one, lead to poor economic performance, including GDP (one of the main indicators). This way, it is easier to launder money or transfer funds outside the country. Neither banks nor payment processors will get their interest.
McCall Robinson a manager of Merchant Accounts, believes that most countries prohibit Bitcoin because it cannot be regulated and he said that. "Many governments do not like the very idea that there is another form of currency that they are not able to control. The supervision takes place on the Internet. Some countries consider it as danger to their society and government.