I don't think that's it at all. I think it's because they expect everything to work the way the phone system did. For a long time, tapping a phone was just a warrant away. And it really was significantly harder for anyone except the government to listen in on phone conversations. Now, the world has moved on from POTS to connections that allow arbitrary data to be sent instead of just sound. In that world, the control in the system shifts to the endpoints and away from the network. We (the kind that reads HN) understand why that has to be the case, but lawmakers and law enforcement are struggling with that paradigm shift.
I see it as being very similar to the problems encountered by the record companies in the late 90s/early 00s. They were comfortable selling CDs and understood CD copying well enough to deal with what little piracy there was. But then Napster came along and showed that their product was just bits that could easily be transferred freely across the globe. We all understood this reality, but the industry spent the better part of a decade trying to make uncopyable bits (DRM) and to stamp out piracy in a torrent of lawsuits. At this point, they've mostly come to terms with the new reality and are adjusting.
Government is going to need to come to terms with that same new reality and adjust.