This is from the national breed club:
I know why the corgi was bred the way it was and in many ways it is a sturdy breed, but they are prone to seriously hurt their backs in a way that dogs of normal height aren't. I also don't mean to sound like I'm passing a value judgment on dwarfism in terms of human beings, but it is a genetic abnormality and does have a number of health issues associated with it.
Many dogs were bred for specific purposes that make them less sound overall, even though they are perfectly suited to the task for which the breed was developed. Any extreme trait is bound to have problems. The giant breeds are a good example of this. Very well suited to the task they were bred for, but fraught with health issues.
The thing is, while a breed may be well suited to a particular task, it is rare that dogs are used exclusively if at all for those purposes anymore. There was a time when a dog was a tool, not a pet. As long as it served it's purpose well the ability to function in different areas was not emphasized.