The thing is, lightning is not necessarily looking for the tallest thing to hit. It's looking for something that it's attracted to due to a difference in electrical charge. The ground normally being negatively charged, clouds being both positive and negative. When the buildup of these charges is great enough, you get a spark between the two - lightning.



The idea of grounding things together provides a path for the lightning, but it also bleeds off charge build-up, helping to avoid the strike in the first place. The principle used is refered to as a "Faraday's Cage". In that it provides a conductive path for the lightning, you could argue that it indeed is supposed to attract lightning, and carry it away from what is in the cage. But again, the technique also bleeds off potential, thus helping to avert the strike.



Check out Chapman Piloting Seamanship and Small Boat Handling for a better description. No, I didn't write it... ;-)



The rockets: The rockets themselves are probably developing a negative charge as they go through the air - the cable provides a path for the strike - same idea, but in this case the rocket is intentionally building charge. A real world case - in 1986 an Atlas Centaur rocket was struck by lightning on launch. As the rocket entered the clouds, it got hit, destroying it and the payload. The strike continued through the rocket body to the ground near the launch pad. Same thing - the rocket built charge as it moved, the charge in the clouds couldn't resist...