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.
I think this topic concerns the technicalities of Bitcoin as a currency. Although it is legal and is already received by many countries, companies and people alike, the fact that it's not yet recognized in a large scale in terms of the number of people who sees it as a legit currency as well as use it for different transactions are the driving forces that hinders it to be embraced and propel it to a wider reach in the business and investment sectors.
There are 2 problems, legalization and spread of bitcoin, you right even though bitcoin has been legalized, but if the number of bitcoin users is a little bit, it will be useless to use bitcoin as a currency because there will be fewer parties who will receive payment with bitcoin, both of that must complement each other..