There are a couple of things I have highlighted on that. Certain countries have embraced it, including Japan, South Korea, China, France, Italy, U.K., and India.
I thought this was an interesting perspective on it:
...in November 2015, Japan sold an 11 percent stake in its postal service, which houses the country’s biggest bank by deposits and its largest insurer. The sprawling operations had become a symbol of government inefficiency and cronyism.
The article was trying to be balanced. It went on to say:
The track record of postal banking suggests a trade-off. Government-run postal banks can be effective in reaching rural and other underserved populations,
—which is what Sandy was saying—
but can also be used to divert savings to investments whose goals are more political than profitable.
That's probably my biggest concern.
Opponents of postal banking argue that getting the unwieldy postal bureaucracy involved in financial services can be a disaster that could stifle startups working to adapt mobile technology and new data tools to serve the unbanked.
There are pros and cons, but I can see that the community hubs model, which is maybe what you're suggesting, could work in certain communities.