It doesn't matter what awesome crypto tech we come up with. It will never see the light of day. Law enforcement shows up at the shop, if the merchant lets anyone walk out of there without having paid in the state currency, he goes to prison. All merchants who are not otherwise breaking the law, being rational, will not risk 10 years in prison just to bypass chargebacks and 2% fees.
The reason I ask is because in my (admittedly limited) experience outside the G7, what I've observed is that as regimes become more dictatorial the willingness of the population to find creative solutions for bypassing the dictates increases along with the totalitarianism.
It's not a concept that people who have lived in relatively free countries would be familiar with, and it's something that it's easier to understand after having witnessed it.
There probably aren't many places where the necessary conditions exist. There has to be both a relatively good state-run system, and a government that can make quick and arbitrary threats of violence.
First world countries can't just arbitrarily declare 10 year prison sentences for anything (eg eating a banana). And dictatorships usually have terrible state-run systems where the motive for people to risk prison is fairly high.