No doubt there are circumstances under which it will reach those speeds, but CNET chose to exercise the battery in the same way it tests notebooks from that other computing platform, at full bore. To do that, they played a DVD, starting with a full charge, and waiting till it ran down. In this sort of test, the battery is being drained fairly rapidly, so it won't deliver the best numbers. In fact, they'll be far less than the maximum rated life, which is to be expected. Not at all.
Processors require a certain amount of power, as do LCD displays and hard drives.
Getting the most out of a notebook's battery is a bit of a juggling match. With a little attention to the things that wear the battery down, you'll get more life. If you have an AC outlet or a spare battery on hand, saving battery life won't be an overriding factor, of course. But computer companies are always going to emphasize the best their products can do. That's the sign of good marketing.