@MiM it's a Jeep thing and I guess you don't understand.... 
It's just a cool feature. It has a pop in panel to make it water tight. It's just another way to enjoy the Jeep out on the trail or just driving down the road.
As to it's origin it kind of calls back to the older CJ5 soft tops. My CJ5 I had in highschool had old school soft top with soft doors. The top had a zip down window and the lower half had a clean windows that you could see out of. It kind of pulls from this old feature.
Jeep didn't have to do it and from a cost standpoint really should have just been killed. What it tells you is there are still people at FCA and Jeep that understand it's more than the bottom line. It's about building on what a Jeep is and rather than reducing cool features they are adding them back in.
Did I mention that with the new 6speed manual, diff ratio and transfer case the Rubicon comes from the factory with a 83:1 crawl ratio and 33" tires... From the Factory!
