One word: Botnets. If everyone that used a computer on the internet was educated in how to avoid downloading malicious software, how to recognize when their computer may be infected, and how to remove said malware, we could put a major dent in the proliferation of botnets, which I think everyone will agree are one of the prime real threats to global cybersecurity today.
Remember: it may take one hacker to program a botnet, but its takes thousands of ignorant people to run one. A little required education could go a long way. The exact implementation of a "computer licence" may need some work, but there are some real possible benefits.