Instead of making it illegal, they should rather look for a way to regulate it such that they can have a little control over it in their country. The issue with government and bitcoin is the inability of government to regulate bitcoin as they want,that's why bitcoin has always been a threat to them. I believe in nearest future a way will be brought up to regulate bitcoin and not declaring it illegal .They have tried a lot to do so from the beginning but unfortunately they never succeeded. As you have seen the ban has imposed many times by the major countries of the world having big crypto community but it doesn't take too long to lift their ban. Now it seems impossible that a worldwide would impose over cryptos because crypto community is now much more stronger than ever before.