why bitcoin is still illegal in many countries of world

Is there any solid reason behind this ??/
Where are bitcoins illegal? China?
Edit Nope.
While private parties can hold and trade bitcoins in China, regulation prohibits financial firms like banks from doing the same.
In the first place there are questions of illegal transactions, tax evasion, money laundering, proceeds of crime. In fact, using the means of payment without necessarily identifying the members of the operation, these operations easier to perform.