philosophy: private conversations between citizens is an important aspect of a free society.
When a society shifts to digital channels, most private conversations occur online.
If those channels are not truly private (protected by end-to-end encryption), it marks the end of private conversations, and in some ways the end of a particular type of free society.
That this shift happened decades ago with in-the-clear telephony is probably less important due to practicalities of recording, storage, and analysis. Those problems have been resolved in 2017 thanks to Moore's law and machine learning.
Letting an out-of-control bureaucracy have god-like access to our private conversations leaves us almost down to one type of private free speech: private speech: '...speech spoken to oneself for communication, self-guidance, and self-regulation of behaviour.'