I think the reason why other ban crypto because crypto is a new currency, unstable, highly fraudulent and has not reached a certain balance like some other markets such as stock, gold .... Governments have not recognized crypto to protect people against scam risks. Once crypto is more transparent and stable, I think it will be recognized and become more popular.
The main reason to ban cryptocurrency is its system where it does have a decentralized form of market that could give people an open option to deal with any form of transactions and form of dark transactions all throughout the web which could include illegal transaction and transactions that against the government or under the probitionary measure. It also gives a good form of opportunity which taken by a government by a threat for bigger businesses that could not give them chance to pay tax on the government and start an investment for an initial earning for people without a help on the government.