I think Post Offices are important. I think this for a number of reasons.
The most obvious is the services they provide. Whilst some of what they offer is available elsewhere, the local post office is still the go-to place for so many things.
The post office is trusted in ways that make them the envy of many businesses. You can trust your local post office.
Service is a word that comes to mind when I think of post offices. An unhurried and genuine service, so often absent in other places.
Whilst mergers may make business sense, depriving a community of its post office diminishes that community, much like closing a library, or public convenience. A community is more than just a collection of customers.