Okay. Umm, why not?
I remember Grant Petersen's infamous 'sword fight', pitting a steel fork against a carbon fork. Result: carbon fork undamaged, steel fork looked like a pretzel.
In a situation like the one above the fork is resting on the sidewalk and the front end of the bike can pivot about the post. An accidental kick from a pedestrian and your bike will be swinging with the fork dragging on the sidewalk. I've actually seen this happen numerous times. I probably should not have singled out carbon as this can damage any type of fork, but people tend to be more sensitive about carbon parts.