I dont know why they bother, its for this reason other manufacturers like Land Rover dont put the plug in as standard, their included with the mats and just need screwing into place.
The problem is what happens if the mats, especially the genuine mats, dont like up with the plug?
Or like us, its a company car and doesnt have mats ... the plugs simply get ripped out of the floor with our feer moving about on long trips