Bitcoin works on Blockchain technology and is decentralized. The transactions made in the Bitcoin network are peer-to-peer i.e., there is no central authority. Not being a legal tender does not mean that you can not use it to make financial transactions. It means that it is not consider as a form of currency and that it may not be accepted by people to make financial transactions. And because Bitcoin users do not require a central authority to make transactions, there is no need of banks to make transactions. Due to this, the government is not in control of any transactions made in the network. This might also affect the revenue that the government gets through the banks. And also, there are no regulations on virtual currencies as of now. The government is conducting research on how relevant it would be to consider bitcoin as a legal tender. But for now, it has declared that bitcoin is not a legal tender.