I'm wondering this because is such a real threat to bank system and we all know how banks and governments are tightly linked !
BTC could make people more autonomous, self-resilient, being their own bank. You can use it like cash, making your transaction almost untraceable (or untraceable using e.g. monero or dash or laundry systems) : this is governments worst nightmare, isn't it ?
Because to ban bitcoin they should pretty much ban the internet, and of course it's impossible. And all the countries of the world should agree, and that's something quite impossible. People would keep using anyway the bitcoin, the ban wouldn't stop them.