The reason that analogy falls short is because it's easier to drive the huge truck at 200mph than it is to find 16 truck drivers. It's really neat when you figure out how to map/reduce your algorithm so you can parallelize it, but it would be even easier if you didn't even have to in the first place. And that's assuming that it is even parallelizable in the first place. Not all algorithms can be optimized like that and needs a bigger system to run on.