The military and certain branches of the government (e.g. CIA) are very interested in having modular, autonomous structures that can survive in the event of a decapitation attack, or if communications are severely disrupted through other means.

They're also interested in having centralized control so the various components of their organization are not running rampant and in conflict with the others.

It's a delicate balancing act. Look at the US as a whole: If states are too independent they might get into wars with the others, not unlike The Holy Roman Empire. If they're too much under the thumb of the Federal government they'll feel oppressed.

If (my example) instead of people messaging each other on facebook, every single person needed to run a server (such as an IRC server) at home - no centralization at all. (If five people want to talk to each other, there are a total of 10 connections because 4+3+2+1 to fully connect every node with every other node). That would be an (extreme) example of decentralization, and obviously centralizing chat so I can just use a thin facebook/whatever app is hugely convenient. Likewise the blockchain is a joke, a single $200 pc can trivially do the work of the entire bitcoin network, trivially - if it were centralized. This second example also shows what is meant by control. So it's a balancing act.