The answer is that people cut them off when they're born.
Why would anyone cut off their dog's tail?
The answer to this question is part tradition, part work related and part tax evasion.
Humans have been docking dog tails for thousands of years.
The first records of tail docking tell of a Roman superstition that docking a dogs tail on the 14th day of its birth would ward off evil spirits and disease like rabies.
At some point later, it became popular for many hunting and working farm dogs to have their tails docked. These measures were intended to be injury preventative. It would be impossible for livestock to step on a herding dogs tail and break it if it was removed at birth.
As dogs became more popular as house pets among the upper class, the government of England passed a luxury tax on dog ownership. The exemption to the tax was if the dog was a farm or hunting dog. Despite any work related need to have tails docked, owners would do so to avoid paying the luxury tax.
Many counties have recently banned the practice of tail docking but the United States is not one of them. Although consumers have become slightly more aware of the issue, there is still a lot of ignorance and the vast majority of pure breed Corgi tails are still docked . Part of the problem is that the AKC breeding guidelines continue to endorse a docked tail standard. This means that Maximus can never win the Westminster Dog Show and most reputable breeders will always dock at birth. Because most owners take possession of their Corgi at 8 weeks and tails are docked at a few days old, they often don't have a choice in the matter. Maximus' breeder was local, very responsive and had a waiting list months long for puppies. When the time came, we were able to pick him from a litter of 9 at a few days old and he was the only one to have his tail spared.