I have heard that they typically do the lower body panels in black or a darker color to give the illusion of an increased ground clearance. You'll notice they do this on a lot of CUVs nowadays.
It's not just that, it's for visual weight and masking of quality of materials, as well as cost control. When presented with contrasting colors like that, your brain tends to estimate them as separate things. This helps it look smaller, and smaller equals lighter, right? Then you have the choice of doing big panels of cheap material, or big panels of good material, or regular sized panels of good material with add on panels of cheap material.
Look at the scion xB in certain flavors. HUGE swaths of cheap body colored plastic, that makes it look bigger. They flex, and that makes the car look cheaply built. Take the soul, and it uses steel body panels with a polymer skirt, all one color. This means you get a bigger look and no cheap flex because the plastic panels are smaller. With the renegade, it will make it look lighter and more nimble, and they plastic skirts will all be black, so other than the trailhawk bumpers, it's one common part in one color for all variants of the car regardless of body color. This is one way to control costs. Hyundai/kia spent money on some really nice robotic paint application, so good paint costs them less than for many other manufacturers.
Another reason more cuvs are going to black plastic for the skirting is hiding aerodynamic features. Shuttered grills are less obvious in all black, and it's a complex part to paint. Adding some air dams is aerodynamic, but not in line with the visual design of the car, so black helps remove the details of them at first glance. THen of course you have the how many grills does this car have and which ones are real. These days the answer to those two questions is 3 and 1 more often. Renegade has three visually, but how many are functional?