That's because paper currency are believed to have value and are also legitimate by the government, so paper currency can be used to buy all your needs. Not because of the paper, but because of the approval from the government and also a belief that it has value.
I agree. This is a means in doing transactions that's why. This is what they consider a way in which currency is known. We can say that this is the legal or the legitimate way to interact with the market. And thus bitcoin is not this kind of thimg therefore it is more effective.