I don't think it is legal anymore to fully dock the tail - someone will correct me if I'm wrong!
Purdey, my springer, has a 2/3 docked tail. The breeder had quite a challenge to find a vet who was willing to dock. My vet disagrees with it and says the spindly tail should be bred out of the breed but I can't see how that is really practical!
I would much rather see a healthy dog with a healthy docked tail than one that is constantly injured/split.
The guys who are into field trialling often leave the tail longer than what you would normally see - its because it can make the dog flashier when competing and hopefully draw the judges eye.
Flyn's tail has been docked too long too - but thats just because it wasn't done at the correct length at the time
Puppies are docked at a few days old, so it may be that the dog was bred with the intention of being worked and then ended up as pet for whatever reason. Or of course they may have actually worked at some point.