The reason behind this annoucement that bitcoin is illegal is because the government cannot contro or manipulate bitcoin the way they control the economy or system of their country. Though not all countries considers bitcoin as illegal many are accepting it also, if you had been reading in our forums, you know about this.
It's not that bitcoin is illegal, in our country bitcoin is not declared as legal nor illegal, government don't recognized it's existence. However there are still merchants who accept bitcoin as mode of payment. Government did not announce its legallity yet because they cannoy manipulate bitcoin and that they need to conduct their own research about it.