Okay, the video was a spoof. Now let's talk about the real reason.
Bark River Knives carefully skeletonizes the tangs of some of its fixed-blade knives to reduce the weight of the handle and, as a result, move the "balance point" forward. Whether a knife is large or small, the closer the balance is to neutral, the easier (and less fatiguing) it'll be to use.
When you pick up a knife that's balanced in this way, it feels like it's an extension of your arm, becoming (as the saying goes) "light in the hand."
And no, skeletonizing the tang has no effect on a Bark River knife's strength.