The only reason governments don't accept it as legal tender is because they don't have absolute control over it. Bitcoin can be mined by anyone. That's like printing your own currency. No govt wants the people to do that.
Such crypto currency will become legal when the govt's start mining their own to save on printing costs and security costs of printed currency. This will take around 15 years I'm guessing. The only reason its holding them back is the enormous power cost behind mining and the limit of a few billion coins. If there was no limit and coins could be generated easily, most govt's would have already started their own countries coins by now.
Such crypto currency will become legal when the govt's start mining their own to save on printing costs and security costs of printed currency. This will take around 15 years I'm guessing. The only reason its holding them back is the enormous power cost behind mining and the limit of a few billion coins. If there was no limit and coins could be generated easily, most govt's would have already started their own countries coins by now.