Whether or not this portion of the doors are prone to getting chipped from rocks, I don't see why it's any car manufacturer's responsibility to make sure it's protected from such wear.
I suggest looking at it from 'the glass is half full' perspective and just be thankful that Tesla is even providing this and, to make it even better, at a fraction of what it would cost to have it done professionally! I happened to recently have the entire lower portion of the doors (everything below the crease) wrapped in PPF, which cost about $500.