this is how governments view cryptocurrency in a "almost" accurate timeline.
2012 - What is this cryptocurrency?
2013 - Cryptocurrencies is a fad and probably a scam. But it's funny that people are paying attention to it.
2014 - Cryptocurrencies have no use case and no one is using them.
2015 - Cryptocurrencies only have small use case and only a fringe population use them.
2016 - Cryptocurrencies is dangerous and will only be useful in 20 years.
2017 - Cryptocurrencies should be banned unless we can regulate(tax) the industry today.
2018 - Cryptocurrencies is an industry going through regulation(taxation) and we are the experts in that field. Refer to us for all information
On another note, It makes sense why governments worldwide want to repress and "regulate" cryptocurrencies and even to a point calling it something it's not (Blockchain, Distributed Ledger Tech etc....). All open cryptocurrencies, especially Bitcoin, have one common aim. To take away power from the government to the hands of people in the money they use. If you use the Indonesian Rupiah, you have to get the money from the banks, you have to go through the banks to send them somewhere far, you have to cash in the money to a bank to get other forms of asset like a business or a property. Everything you do is taxed by a government, whether you like it or not. And no i'm not talking about regular taxes (which you should pay btw, thats how roads get paved). I'm talking about the sheer robbery of value in your money in inflation. $1000 10 years ago almost $1200 today for the same value. When governments print however much they want, it's the people who hold the money that suffers.
Cryptocurrencies represent a choice to hold your value away from government inflation. That scares the government. Because once again, something is coming to take away their power.
The PRIMARY responsibility of Governments Worldwide is to act as regulatory buffer between Constituting entities aimed at forestalling conflicts which could snowball into Crises.
Cryptos, originating from Private or Corporate entities, beside Government, because of monetary incentives would compromise it's operation to their undue advantages.
Also decentralized payment systems like Cryptos which negate and thus render ineffective international commercial engagements between Nations. Similarly, Governments, would not be able to monitor and tract international trayies and finances. Cryptos could also be used to finance Terrorist Organisations whose operations are inimical to the interest of Humanity.
Most of the things (and problems) in our life happen because of money. We cannot get food, water, clothes, house and other means of living, unless we have enough money to buy things. Money is anything that can be universally accepted and used by people as a means of exchange of goods, services and resources. What will happen if everyone issues his own currency? Certainly, it will be a state of chaos and uncertainty. Currency issued by one person may not be acceptable to others because others would like to give or take their own currencies. Thus everybody will push others to accept his own currency. So, it will not fulfill the condition of 'universal acceptance’. Hence, this task was entrusted to the governments, so that currency/money issued by one entity may be accepted by every citizen without any hesitation. Also, a government has the power to force people if they don’t accept money issued by it. So, it is a prime responsibility of a government to issue a currency; maintain its supply and stop people from making counterfeit money. Government does it through their central banks and law and order making agencies.
Cryptocurrencies are changing this scenario. They are creating a parallel system of issuing money and also enabling people to buy and sell money with no restriction. Everyone is free to run his own blockchain and issue cryptocurrency on it. That is why we have over 3000 cryptocurrencies and tokens available in the market while every country has just a single currency operating inside its boarder. So, governments have to check this state of chaos. They cannot afford someone to disrupt the whole economic and business structure.
Fiats are issued by central banks and central banks also control their flows. From central banks money reaches to commercial, merchant and other banks; and from them to us. These banks and middlemen earn a huge profit in the form of the transaction fee and interest.
Privacy, anonymity, quick transaction and removal of the middlemen (banks) are striking features of cryptocurrencies but criminal organizations and wicked people can exploit these features to transact money for conducting their illicit businesses. Money laundering, smuggling, terror funding, drug dealing etc are some illicit businesses that are getting advantage because their transactions remain anonymous and hidden from the authorities.
Crypto boom of last year (2017) gave a fair chance to the scammers to issue fake ICOs. Many lost their hard earned money because of them. It is the duty of the governments to keep people safe from scammers.
Also, cryptocurrencies can enable people to be self-dependent. It can weaken the position of governments. Governments can lose their authorities over people on account of it. So, they cannot afford crytos to undermine their position. Governments are run by powerful people who will never allow people to be free from their clutches. This is another reason that governments are trying to control or regulate cryptocurrencies. It will make them safe against the danger of losing power. After imposing regulations on cryptocurrencies, governments can get taxes from crypto transactions and also can get the exact data of the persons who transact money through these methods. So, these are the reasons that governments are trying to control, regulate or ban cryptocurrencies.