Out of 195 Countries we have today ( Globally ) All countries have their own forms of Government. Making it Illegal is just difficult the whole United Nations has a lot more in their bucket to do than putting more attention to Bitcoin.
Instead of them thinking about issues that don't matter to them so much. Different Countries are better off fixing their own issues. Bitcoin to begin with doesn't have direct impact to the economy ( yet ) so they should have no grounds of doing so.