So does this work for snail mail?
I'm concerned that some people are using Royal Mail for illegal or nefarious purposes, even perhaps sending copies of CDs or other such malfeasance. Perhaps every "packet" should be inspected, just to see, and so we can notify illegal users of the service and have their letterboxes nailed up. Or perhaps just shrunk a bit - maybe we break one of their postmen's bike wheels or something, you know, slow the service down. That'll stop 'em.
If I can't have a reasonable expectation of privacy of data I send via the internet, I don't see why I should expect greater privacy through a more traditional method of data transfer, or why the current government types think there should be a difference between the two.