For starters, it's exceedingly practical. This isn't a tiny driver that will save you six grams at the cost of a new chain a month, or a titanium-shelled plastic peg that will serve no purpose whatsoever. This is something that will save you from the embarassments of skunk stripe and wet pants, plus protect the bolts in your seatpost clamp and Primo Rod.
Secondly, it's a product that actually requires a bit of seatpost. You're not going to run that with the Macneil Nub.
Thirdly, just look at that bike! There's someone who doesn't care much about fashion—or someone who's been in a coma since 2001. Note the giant Kink sprocket, the sprayed DK Iron Cross pedals, the torn Hemmorhoid (ouch), the dinged-up 48-spoke rear wheel. Other than the tires, there's a bike that hasn't been upgraded since Trend was still around. (Although that was a "limited" sprocket when it was new, so obviously our rider wasn't completely immune to the bite of the hypebeast. Well, either that or he really wanted a gold sprocket.) Anyone want to venture a guess as to what kind of frame that is? Metal Kizz? Old Barcode? It's hard to tell without being able to see that seatstay junction.
All I could think of when I first saw this was the end of Taj's section in Forward, when he blasted through that wet drainage ditch and threw that downside whip. If only he had the Matt Wakefield Signature Mud Guard. Of course, if he did, one suspects it wouldn't be a Matt Wakefield signature product.
Wait, am I thinking of a different video?