This is the gov world though, where the interesting information is things like your address book, your emails (the content as well as the senders/recipients), y

This is the gov world though, where the interesting information is things like your address book, your emails (the content as well as the senders/recipients), your private keys and passwords, etc. etc. Client sides provide direct access to those things (or at least, a means of obtaining them). There are very few governments that care about what is on your company file server or in your company databases. (Ignoring the elephant in the room on that one.) Law enforcement agencies keep huge Access databases of the contacts they extract from cell phones taken from criminals. They share this intel with each other via email (I know, I know...). They can discover a great deal about who is involved in an activity and where they are on the totem pole from just this data. Its even possible to identify people by correlating the content of the "name" field and using the phone number is a unique ID. Criminals tend to have poor OPSEC.