It is argued that it is unreasonable to allow or create an exception and therefore this daft rule must stand.
There are lots of exceptions in rules and laws.
We can't drive into a box junction except when turning right.
You are not allowed to smoke in a work place, except in a prison.
You are offside, except when the ball is passed from your own half'.
It seems a fragile and unconvincing argument to suggest that creating an exception will open the floodgates and that we can do nothing about it....