Cryptography can protect stuff once it's going over the wire, but there are other kinds of threats that cryptography doesn't necessarily protect against. Cryptography by itself is not the only tool that's needed to secure a corporation's information assets. Another is firewalls. Corporations want to protect their legacy systems on the internal net. As they connect their internal net to the external net the firewalls help protect the internal net, which may have old machines without very good protection, from malicious hackers that may be coming in over the Internet.
Digital certificates are one of the key technologies for getting public key used pervasively.
You need to know that you've got the right public key when you're authorizing somebody to log into a computer system or when you're executing a digital transaction. Digital certificates are your Internet calling card if you will. And they're going to be essential, they're going to be widespread, there are going to be lots of them, available in lots of places. You need it whenever you're communicating remotely to make sure you're talking to the right party. And so much of our communications will be remote, over the Internet.