Can we get rid of banknotes and coins? this is more a theoretical question, nowadays with Internet, Debit/Credit cards and Cryptocurrencies, why should we keep printing/making more physical money? 

granted not everybody has access to these technologies, but for the sake of this question, let's say every body does
Money will always be used for exchanges between nations. As a universal equivalent it will still be the best commodity for nation-to-nation exchanges and for measuring debts and credits between nations too. 
Besides using alternative open source equivalents, such as cryptocurrencies, how would national banks manage to regulate inflation rates? This certainly is a critical point. Bitcoin for instance is a finite source of exchange: if it were to become a universal equivalent, virtually it would infinitely increase in its value, since the volume of the market exchange gets bigger and bigger.  Other cryptocurrencies tried solving this creating non finite sources, yet this still implies a arbitrary growth of the volume of available currency.