Over the past few years PGP has got thousands of adherent supporters all over the globe and has become a de-facto standard for encryption of email on the Internet. The InterNet is based on trust.
Most information is sent over the wire in cleartext.
Every time you log onto a server via telnet or ftp - your passwords are sent cleartext. All email are sent in cleartext, and so on. Most of us send emails we don't want anyone but the intended receiver to read. Everything from passwords to secrets that must not get into the wrong hands. Since the InterNet is as insecure as it is - you need to garble the text in a way only the intended receiver can understand.