you can sorta tell in my last picture, how the side skirts sit lower than the bottom of the front bumper.
maybe its just me, but unless its a full out race car (where the rear bumper usually sits a lot higher than the rest of the car's body panels), it always looks really awkward when one of the body parts sits at a different height than the rest. whether it be the front or rear bumpers, or the skirts/rocker panels.
the chin spoiler seems to even out the overall height of the bottom of the car, making the front bumper sit even with the skirts and rear bumper.
plus, i know some people like it, but i always thought the GT/v6 bumper just looks goofy, like it has no aggressiveness to it at all. at least the chin spoiler makes it appear like it has a "scowling" look to it.