Well I went out and searched around about lightning rods and there are a lot of theories, not many of them agreeing with my physics teachers' explanation. But I did find one that seems to meet what I see as the right reason. And whoever said it was right, lightning comes up from the ground and not down from the clouds. A lightning rod is more for providing a safe path to the ground in which nothing will overheat rather then to prevent them. Try this.
http://science.howstuffworks.com/lightning9.htm M@T
