Remove paper currencies in general to crack down in spending that is not state sanctioned, and to prevent money laundering and capital flow where it is not allowed.
China's cashless revolution (WeChat & AliPay) are a great case study: (public dgaf about privacy) + (govt wants to track all people all the time) = terabytes of spending data per day
Combine that with their Social Credit and total automated surveillance of all activity (All activity tied to ID, games,tv,internet, you name it). Automated tracking of all assoiations.
Tinfoil hat time: China hasn't rolled out cameras + facial recognition only cos Chinese tech is still largely ripping off western tech & western FR is notoriously bad with Asian faces