Hm, it is a very tricky situation and will always be argued!
Personally - If I were to buy a rottie or boxer etc I would not mind that it had a tail. It is strange to see them now that it is no longer allowed but it is better (especially with generally more dominant/confident breeds) for body language, that they have their tail as their moods are then easier to read.
From a working point of view - It is much nicer for the dog to have it done quickly and easily as a puppy, rather than wait and see if they damage their tails through working and then having them go through that initial pain and then going under the knife to get the job finished.
Also as man like to mark their territory in more physical ways, eg: barbed wire. You do see some foxes getting caught and tangled by their tails.
I do think it should still be allowed for working dogs, not working BREEDS as some will be sold on for domestic ownership, but simply for the dogs that will be used in the feilds.