Ah the question we Aussie folks are constantly asked. First of all, Aussies can be born without tails. Many can have no tail, some with a range of half length tails, and some with full tails. Its in the genes. Why then do we dock the full tails? Well, first of all Aussies were bred for livestock/ranch hands. Many work long and hard in all weather and in all kinds of terrain. Its not only easier to keep a dog cleaner, easier to keep the dog from being injured, but also easier to keep the breed standard (if everyone is docked then there won't be a variation in the ring). Plus Im glad I don't get whipped to death by a tail (as Labs tend to do) . Has anyone ever slammed their dogs tail in a door? Fence? Car? If not, your dog is lucky. Docked tails are so much easier to keep clean and keep from being caught in fences, doors, etc.
Why are those puppies screaming?? Because they are being taken away from their momma, siblings, and a warm place. There is no nerve endings in their tails when they are docked (if done properly). So you aren't hearing them scream out of pain. More like screaming out of discomfort from being away from their mom/safe place. I have worked for a Vet and I will tell you cropping a dogs ears is more painful. The worse part was getting the stitches out of their ears. Or the infections that came along with it. I saw so many dobermans with sore, raw, and painful ears. I felt sooo bad for those puppies. So don't feel bad for our docked dogs tails. There is more suffering with going thru hip repair, spay/neuter, etc then a minute of being away from their momma and having their tail docked.