It is against the law in England as from April this year, however you will always find someone who will do it, but the dogs will not be able to be shown if they have been docked after this date.
People are used to seeing these breeds without tails, so they view it as normal, and think it strange when a dog has a tail, over the last few years more and more dogs have not been docked, so I have seen lots of these breeds with tails, I like them.
I agree sometimes tails will need to be amputated for medical reasons, I know 3 Labs with no tail for this reason.