Do you think is because of the risk involved or bitcoin increases corruption..
What else
Your post tittle look like bitcoin has been banned, and please try to make your "post tittled" straight. However, bitcoin and altcoins are new technology that has come to revolutionized the ways things are done, eg transactions between mr.A and mr. B.
Now, that lack of central authority is the primary reason governments are afraid of the cryptocurrency.
Governments control fiat currencies. They use central banks to issue or destroy money out of thin air, using what is known as monetary policy to exert economic influence. They also dictate how fiat currencies can be transferred, enabling them to track currency movement, dictate who profits from that movement, collect taxes on it, and trace criminal activity. All of this control is lost when non-government bodies create their own currencies.