Removing cash will be a problem, not every citizen of the society will be able to use online payment. And talking about cryptos, it is more complicated as of now. China has a huge population and it's not possible that every citizen is qualified to send or use technologies like this.
Moreover, e-payments are usually popular among the young citizens of every country. Mostly, Old people are still orthodox, quite a few of them have coped up with the advanced society.