PGP enables you to send e-mail that can only be read by the addressee. And it's no one's business but yours. You may be planning a political campaign, discussing your taxes, or having a secret romance. Or you may be communicating with a political dissident in a repressive country. There's nothing wrong with asserting your privacy.
Privacy is as apple-pie as the Constitution.
When you write a letter, do you seal the envelope, or leave it open. Some think of PGP as merely the equivalent of sealing the e-mail envelope. It's FREE for non-commercial use. Even though you encrypted it, you can't decrypt it. The word cryptography simply refers to a method of disguising the contents of a message.