These cryptocurrency implementations along with some infrastructure would let you build a cheap low-cost micropayments system where you would just need to have some local trust. You could build out a federated payment network and build out infrastructure based on needs. All while avoiding the massive waste that comes from "everyone store every transaction ever"
The problem of credit card companies and the like charging really high rates still affects a lot, and "Paypal, but federated" could help tackle this with some cryptocurrency concepts in the background.
Though to be honest, I don't think this is going to happen. The communities are so focused on completely trust-free models that they don't see how they could build something extremely useful with way less cost and more utility by being more flexible on that point