But... Don't forget that we all put our letters in envelopes (even innocent letters to mum), we don't send them open so that the text can be read by anyone. Privacy doesn't necessarily mean illegal activity. Some things must be kept private, and I hate it when this privacy is violated.
Emphasis mine.
Something that always amazes me about cryptography in general, is that it allows us to control our privacy without sacrificing utility. I can send a digital "letter" that's encrypted, on the open net, without fear of it being compromised (assuming your keys are safe)