As Ponchoshop noted, racing applications have the master switch (not a quick disconnect but a high amperage switch) on the positive side, in an easily accessible location and well marked to allow someone (pit crew, fire or corner marshal, etc.) outside the car to cut the power in case of a crash or fire. Wired correctly, the engine will also be shut off and reduce the chance of fire or further damage. Wired incorrectly as I've seen quite a few, the alternator will continue to supply juice to the engine even though the positive lead has been effectively cut and defeat at least part of the purpose of having the master switch, that of shutting off the engine.

So it does make very good sense - for racing classes. It is a very important safety item that likely has saved many lives. Since you're not racing, do it the way that makes the most sense to you!