Some governments ban the bitcoin in their countries because they have a negative thoughts here on bitcoin. They choose to ban it in their country because they think that the bitcoin cannot help their economy grow or maybe it can destroy their country. Some country have a transactions with other country of bitcoin, So it is the one of the benefit of bitcoin. Also the bitcoin can help their country or their economy grow and have a better country.

In my opinion, I think the goverment ban Bitcoin to prevent illegal activities come from terrorists and money laundering because Bitcoin is used wrongly.
In additional, the government ban Bitcoin to protect the investors in country don't lose their money in this risk investment.
There is a lot of reasons so that the government ban Bitcoin. This is a innovative technology, if ban it will make the country outdates in a world that changes, so I think it's just a temporary method.

I think it would be helpful to improve their economy of those countries who legalised this.l think for development of any state is necessary. so l hope it would be take a time to legalised all of the world.

I do not think you are right. Governments are things that can have a big impact on the price of Bitcoin. By 2017, China has declared ICO banning and prices have fallen sharply for several days

indeed a lot of countries are denying the presence of bitcoin and I think the benefit of the ban from the state is the country's fear of financial disturbance by bitcoin system with decentralized system.

Government will benefit a lot if they ban bitcoin. Without being told bitcoin have already disrupt many services even though it's not fully legalized. Imagine what will happen if it becomes a legal tender. Incase of remittance,  services like western union takes certain percentage to deliver money and at the end delaying before delivery. Many remittance will be out of business if bitcoin is allowed thanks to blockchain technology.

Your question awakens the question, what is the purpose of government or governance?
Off course the simple response is that government is a protective appatus of the people, usually "made" by the people. So, the government is usually responsible to its citizen. They have not really given their support to cryptocurrency because of fear but I'm certain that they don't have option because, technology and innovation is the order right now.

Some countries would ban bitcoin as it has a monopoly on money printing and does not want any interference whatsoever.  Could you imagine the Federal reserve just letting Bitcoin walk right in and take over?  No more milking the populace.  They are either in control of Bitcoin (which I think) or Bitcoin will only go so far.