Clipping versus hand stripping
A terrier's coat was originally its natural defence against predators which lived underground. So terriers were bred to work prickly hedgerows chasing these predators which had large claws to dig underground. So, the terrier who hunted them had to have a specialized protective coat. Should the dog be attacked, this coat had hair that would come out easily, leaving the dog unharmed. So huntsmen selected a special non-moulting coat that became the terrier's defence against the pickles and the predators it was bred to hunt.
Today very few Terriers hunt predators that live underneath the ground. Nor do they hunt in the thick undergrowth of hedgerows and prickles. However, in the modern world the Terrier's coat has become an integral part of their breed type. With no predators or thick undergrowth to pull the coat out, the method of hand stripping was developed as an extension of a natural moulting process. Terriers do not naturally moult. So, their coats do not fall out all over your clothes and carpet. Rather, the older coat has to be 'tugged' out. This process of tugging the old coat out is called ' hand stripping'.
Advantages of Hand Stripping
Hand Stripped Airedale
When hand stripped, the body coat not only looks good, but it is also very healthy. Hand stripping removes the old loose coat, leaving the new body coat behind. If however you clip the dog all over, you cut the old hairs, leaving their roots within the follicles of the skin. This can irritate the dog and be a primary cause of eczema in a terrier.
With this type of coat, the richer colour and the correct texture are at the end of the hair, while the paler and softer hair nearer the skin of the dog. So, when clipped, this type of coat grows back pale and more like a carpet than one that is hand stripped.
Hand Stripping an Older dog
If you decide to hand strip an older dog, you will be rewarded with maintaining a beautiful coat, free from irritations. But if for any reason find hand stripping the older dog a bit of a drama for either you or your dog, a satisfactory compromise is to hand strip the body coat, and clip the tan areas. Alternatively, you may like to strip some of the longer hair of the coat and just leave the new hair behind. If choosing this option, it is important to keep up the 'undercoating'. This is what is called 'rolling the coat'.
References and Further Reading
 Jane Harvey, DVD "How to Groom an Airedale" Rangeaire Vision, Victoria 1985, 2004 ISBN 978-0-9804296-0-2