Now that I look at it a little closer, I wonder if they smoke their rib roasts. It looks like there might be a pink smoke ring on the perimeter. We used to have a place here that served smoked prime rib on Friday nights, and it was out of this world.
It still doesn't explain why they would remove the crust, unless maybe their cooking technique leaves too much char on the outside.
Look at the photos below of a smoked prime rib. In the bottom photo, you can see the smoke ring, which is similar to the photo above. The top photo shows it before slicing and trimming.
Now personally, that charred crust wouldn't bother me. But in a restaurant situation, I can see why they might be inclined to trim it off.