Bitcoins is not yet a legal currency cause not all countries, world bodies have accepted or recognise it. You wrote so much and how come you fail to understand that this coin cannot be controlled by anyone, no one can manipulate it and most of all governments cannot find out who owns it or make you pay taxes. There is a huge hassle process and it's expensive to track it, make a whole set of laws. You get the point don't you.
That was indeed true. Bitcoin is not a legal currency because it is not accepted by most of the governments of each country. In addition, it is not centralized and regulated by them. The transaction is unknown and also the developers. Moreover, bitcoin is not created and implemented by the government so it cannot be legalized.