It looks like that cuz of the angle of the picture and the angle of the rear wheel well. The interior edge is several inches towards the front compared to the outside edge. I did not get in on this buy but have a set nearly identical to these and bought them for this reason. Aerodynamically, these pull air from the center of the car and sends it out behind the back tire. The fronts are similar but not as drastic.
If the camera is held approximately 6" from level ground, they would look level.
Thanks for the pictures, I love the look
and they're not $50 a piece!!!