The main reason to fold it down is to be able to crawl through brush, low trees, under rock ledges, or just to see much better.
The windshield on the JL/JT looks stupid when it is folded down, and it does not get completely flat like on older jeeps. Delicate parts are exposed. The front part of the roll cage is still present. This makes it not any better for traveling through brush and low trees, and in fact there is more danger to get thousands of dollars (factory parts and dealer labor) of damage.
I did fold down the windshield once on my CJ-5. It went back up immediately because I would not drive a long distance without a top and a good way to safely store the removed top at the destination.