Z speed sells them too

 

Is it purely for aesthetic value?

 

Pretty much, but also for convenience for oil changes if your splash pan didn't come w/ the folding hinge.
And if you're lowered it might look pretty cool blowing sparks from under the car when you scrape on speed bumps, etc

 

More than aesthetics - the stock piece will eventually sag, then rip out and down from your bumper. This will protect the oil pan from road debris, makes oil changes a breeze, supports the front bumper at high speeds and keeps the bumper holes from being ripped out when the stock one goes.

 

bumping old thread. This undercover is great in protection if you are lowered. I am on KW V3 and always afraid of what will hit or damage my oil pan. Fear no more!