How about this reason? The tip is centered directly in the middle of the cylinder dome for equal controlled flame kernel dispersion. With a multi tip plug the spark is no longer centered and now your combustion is firing at a different point in the cylinder randomly, which can cause hots spots that lead to pre-ignition, or detonation, or combustion flame kernel issues. Where the position of the spark fires in the cylinder effectively changes the ignition timing slightly. Engineers designed the cylinder domes a certain way so that the plug fires in a certain location consistently each time for most effective combustion.
All that stuff is marketing hype. Only way you'll get a bigger stronger spark is through a CDI module and an ignition coil pack upgrade.
