Total removal of fiat from the society will do more harm than good.
No matter the level of technological development, not everyone will be able to embrace cashless transactions. And also, most services need to be paid in cash.
We don't really know what new technology may come out in the future though. It's possible that somehow in the near future, everyone will have instant access to a bank account or some form of savings account that they can use instantly with some piece of technology. For now, however, I agree with you that the removal of fiat would not fare well with society.
FIAT will be extinct? The entry of digital transaction on the trading market had some effect on the financial Business community, the Fear or apprehension to the future of any transaction using crypto currency or digital is very visible to the business world, but, with the issues concerning crypto currency replacing FIAT money transaction still need to be resolved by the government financial Chief, by the World Bank and by the business community. The issue on regulation in crypto currency or digital transaction is under going tremendous scrutiny by its government. we don't really know what will be the possible effect it the come for the extinction of FIAT money. For now, i would say, FIAT money is still very much needed for any transaction for our daily needs, not only for investment.