Tools of the trade.
Attempts to insure privacy are at least as old as the attempts to snoop, and they come in all shapes and sizes. Years ago sending e-mail via an anonymizing server in Finland made it possible to send a message that couldn't be traced. Personally, I never knew just why I might want to send such an anonymous message (my own paranoias run in slightly different directions) but I can understand why it might be a useful tool. That server, however, is no longer available, though that's apparently due to the fact that it's no longer needed - others have taken its place.
And for those who don't want to go to the trouble of anonymizing their mail, encryption offers them something else to go to the trouble to do. Though I'm really not much of a tech-freak, I do like experimenting with various technologies. Still, I was a bit surprised about seven years ago when a friend (also involved, back then, in learning via the internet) assumed that I had a PGP key. I didn't, and this time he was surprised. The idea of encryption definitely interests me, but here as well, I can't seem to think of anything that I might want to send via e-mail that would demand it.
These examples are from the almost distant past. I'm sure that newer ones exist, though I admit that I don't really have the strenght or the desire to seek them out. My guess is that not much has changed - these are still pretty much the basic ways of keeping something secret.
Go to: They've got a little list.