It is not an easy way to ban BTC for the government  since it is accepted by economically  and technically developed countries . Government cannot shut down Bitcoin through technical means also since it is operated through the means of internet only and it is a digitized and decentralized in nature. The only way to ban Bitcoin is  by spreading rumors about Bitcoin and the negatives of Bitcoin into the mind of the people  so the people may keep away from  Bitcoin.

You stated the answer yourself. Bitcoin can be used for illegal transactions by criminals because they will be untraceable and anonymous (but as far as I know, it is now possible). It can be used for money laundering and other terrorist acts. But because of a lot of people and politicians believe in the capabilities and how helpful bitcoin is, governments find it hard to make it illegal.

it is impossible to do if only a few countries do that, it will be worth it, I think if you want to make illegal bitcoin in the whole world there must be a world institution that consists of all countries that agree with bitcoin in the legal

They can't ban it globally because they don't know how to. It's quite simple if you look at it. Nobody can ban bitcoins because blockchain technology is virtually untouchable. Plus, not all countries hate bitcoins. Some have already accepted and integrated bitcoins to their day-to-day lives.

This is only a very early start for the government if it wants to make illegal bitcoin. There is no real reason to make it illegal. For now, far from threatening banks and governments. If so, the government can regulate its use, not prohibit it completely. Because bitcoin can be utilized to help the economy.

Not all governments think like that. Many are neutral about allowing or banning cryptocurrency in their market and some smart ones encourage and recognize it as a real currency like Japan and South Korea. Cryptocurrencies can be threat to banks but to the economy. Furthermore, cryptocurrencies common goal is to improve the economy by proving a practical and efficient monetary system.

Most governments see Bitcoin as a threat to the national economy due to the fact that it cannot be taxed, there are also claims that it feels crime as outlaws tend to use BTC to pay for their illegal activities, some governments has however allowed BTC operations in their territories while most still haven't. But it all depends on the policies of these governments as they operate on different principles I believe that as soon aas the legal battles are handled, there will be higher chances of BTC being llegalized

There is no central government that rules the world. Just as there are countries with Bitcoin illegal, there are also countries with Bitcoin being legal. The governments do not have the same minds, goals and vision. Bitcoin will continue to reign till it hits a global patronage.

No it's not possible for the whole world to make the decision to ban Bitcoin. What other government see in Bitcoin that could help them might not be seen in another country which is normal. Not everybody thinks in the same manner. Some government sees something good in Bitcoin then adopted it while others sees it as a threat.

Many government show their negative attitude towards Bitcoin and ban it in their respective countries and this is some reason behind this. Bitcoin decentralised nature is the one of the main reason behind this. No government never want something in their country which they cannot control and because of decentralised nature government has no control over Bitcoin. This thing ultimately affects their country economy and financial growth. Bitcoin irregular production and distribution also affect an currency own price in the international market. Bitcoin is also associated with some serious criminal activity. So these are some major reason behind this topic.