The problem with going cashless is that not many people will be able to embrace it. in the advanced countries this may not be such a big deal as nearly everyone is already familiar with all sort of technology and buying online in a cashless manner. in the developing countries with high number of uneducated people, this can be a very big issue, it will require teaching almost everyone on how to operate an internet enabled device and own one as well.
Going completely cashless will pose a lot of challenges to many people which i doubt the governments are ready to subject its citizens to. So this is not advisable best thing for now is operate in both ways
The first impression I got after reading OP is this. EU and USA are not the whole worlds. There is a vast area of land in Asia, and Africa where people don't have an internet connection and are out of the digital landscape we live on. Paper cash is still the only way of the economy there so if mass adoption of cashless policy has to be taken then there should be some measures taken for those people.
On the other hand in many urban areas internet connections is not that strong and secure. A cashless economy means no paper cash. So any disruption in internet connection would cause major damage to the economy.
Cash is still a necessity, which would be difficult in a cashless world. In my family, grandparents are quite old, using the phone and internet has become very difficult for them, so they still choose to use the old methods for daily living. And not only in my family, there are a lot of older people like my grandparents who won't be able to keep up with technology trends they still need but traditional means to serve their daily life.