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.
And I just add to what you said its decentralize so expect that other countries not accept crypto because they know how risky is to their people but like many people said that in here it depend to us what and where we use the earnings from crypto. We can't blame some countries and their government because they don't that their people will be in trouble.