Any given state actor will have full control over some networks. It's fair to say that any given network is fully controlled by at least one state actor, possibly more. It also stands to reason that each state actor has many more networks they can passively listen to. [EDIT: clarity]

Ultimately, if your threat model is to protect against the actions of a state actor who likely does not have active control over your network, but might be able to passively listen, then ubiquitous encryption helps a lot with defense in depth.

A more mundane case is free wifi at an airport. Someone can set up a hotspot with the same SSID and act as a MitM, but it's not undetectable. Here, encrypting application traffic is just one solution, and not necessarily the best one, but you shouldn't be relying on only one layer of protection.