Here's the deal. It's a legal issue. I ordered some (Givi-made Kawi side cases) about two months ago - on sale. They weren't in stock at the shop though. They originally told me they were on backorder, then when I didn't hear anything after a few weeks I called back and they told me that Kawasaki was in legal action regarding the the use of the cases - they covere-up the on-bike reflectors. I just called Kawasaki customer service yesterday and they they told me that the DOT has required some form of reflecting device to be fitted to the sides of the cases before they can sold again. Kawasaki said the time-frame for the backorders to be filled is indefinite.
Regarding the question of the use of the Kawasaki provided trunk rack and side case rack - The rear trunk rack is made by SW-Motech. The sidecase rack is made by Givi. Kawaski specifically utilized this combo to prevent possible overloading of the bike by ostensibly making the two incompatible. However, all you have to do is cut-0ff and file down the grab-handles on the side case carrier racks, then mount the SW-Motech trunk rack on top of the side-case mounts. I know this works as I did it - I happenned to get a VERY good deal on the two racks together when I bought the bike. I prefer the SW-Motech rear trunk rack to the Givi made rear trunk rack anyways.
I hope all that provides some clarification.