If you have noticed, more countries are moving away from cash and prefer bank cards. It is easier for the government to account for electronic money than for cash and coins. The government would also like to know how much money each citizen spends per month; this can be tracked with card payments, but not with cash payments. You may have witnessed that most wealthy people make cash payments because the money was earned illegally, so the government does not see the real income of a person.
Throughout history, the global community has strived for a single currency. If you look at exchanges, some require KYC while others do not, and governments require exchanges to provide a list of their citizens for income transparency. Considering how many exchanges are in the market, each government would have to request a list of citizens from every exchange, which is quite a lot of paperwork.
To facilitate all these processes, a single currency is needed, and that will be Pi.
For those who have not yet installed Pi, you can download it from Google Play and start earning Pi, invitation code: vsembonus.