A lightning rod doesn't really attract lightning. It creates a path of least resistance from the top of a building down to the bottom. A lighting rod is nothing more than a long stick of metal that creates a conductive path for charge to travel. Lightning striking a lighting rod travels safely down the building to the ground, decreasing risk of fire and computer damage to the building. The main purpose of a lightning rod, however, is NOT to attract the lightning. The main purpose is to slowly leak charge down to the ground to avoid a lightning strike. In some cases too much charge still builds up and there is a strike. In the case of a strike, the charge is safely transferred to the ground.
Avoiding the strike to begin with is the best option, thus the main purpose of that lightning rod is to leak charge, not attract the lightning.