Convenience is the key here.

Syamntec, McAfee, and others stay in business by making people believe the annually recurring fee they charge will protect them.

Phishing filters, spam blockers, spy ware scanners... snake oil.

I will admit that I use virus scanners, but I also know how to secure my home pc.

The problem we face with the mass is that its not convenient to learn. Its more convenient to spend $$$ and pretend they're protected.