The answer to this one is obvious. In order to grow, a replacements need to interoperate, ie. provide an "upgrade path". Instead of holding something up as the one true solution we are betting on the trend, which is certain. Besides, cash will always be around.
Cryptocurrencies, despite their huge number and numerous attractive properties, presently lack market depth, limiting both their stability as value stores and feasibility as trade instruments outside of rapid/realtime/automated exchange. Significant issues with the dominant one (Bitcoin) make it difficult to implement securely, hard for non-technical users to properly understand or trust (there is no benevolent dictatorial regulator, as per their established national currencies/financial service providers), they require connectivity or blockchain storage which is unvailable in much of the world's devices, and so on and so forth.
A parallel to your suggestion is the example of existing community currencies, which are essentially geographically bound equivalents of cryptocurrencies with an often more moralistic focus. I have been in contact with these groups and associations thereof, plus theorists in the area, and my understanding is that many face challenges in the same areas as Bitcoin; ie. new user education, balance of trade and interoperation with conventional established systems. Indeed, they are developing an inter-exchange protocol at present known as CXP.
As for your vast simplification, the best (from a moral standpoint) and hardest kind of change to reverse (from a potential opponent standpoint) is that which is is completely decentralized; an 'opt-in' from the edge nodes. I think this is what people are proposing in many spheres right now.
All roads lead to Rome.