The most common reason governments say when they announce to ban or sanction anything in blockchain and cryptocurrency is "It is used for criminals".
Before introduction of cryptocurrency money laundering is already in existence, but since the introduction of bitcoin in 2009 bitcoin has be established, and its obvious that governments seems bitcoin as one of major elements use to extort money from people and also seen Bitcoin as easiest way of committing money laundering whereas before bitcoin existence all this things is already evokes or exist, so the thing is governments is against bitcoin and that's while they wants to allow bitcoin stand firm, but the situation and the level bitcoin has been, I believe that bitcoin can no longer been destroyed by government.
See what banks are used for?
For criminals.
And how much some parent companies of banks had to pay for penalty?.
The is alot of irregularities or illegal act's going on in banking system but governments can not concentrate to figure out those irregularities in banking system, but I don't know while governments refused to fight banks while illegal things is going on there.
Why governments don't ban banks even banks are used for criminals?
Why governments don't ban knife, gun, email producers/ companies because they are used for criminals?
governments don't want to ban banks because they feel banks operating system is centralized while bitcoin is a decentralized way of banking system in cryptocurrency, they can easily access banks and also figures out the database, while the privacy in bitcoin is what's makes them to feel uncomfortable with cryptocurrency, for example when you transfer money from one bank to different banks and brand, it will be easy for governments to detect and monitor how the funds went through, but in cryptocurrency mostly Bitcoin when use mixer to mixer your coins, it will be difficult for governments to trace the transaction history, and we know that with mixer it can be traceable, so that's one of the major reasons governments fights existence of bitcoin.