Whenever I arrive at a consultation and see an extendable lead, it is virtually guaranteed that the dog I am about to meet has no lead walking manners. Small dogs often dart left and right, creating a trip hazard. Larger dogs can lunge towards anything interesting and pull the owner with them.
Control
When out in public, it is important to have good control of your dog. Using a standard lead keeps the dog nearby, making it easier to pass another dog, squirrel, child, skateboard or road safely.
Body language
A dog pulling hard on a lead can display body language that causes tension with other dogs. On a long lead, you cannot act quickly enough to prevent trouble.
Risk of injury
Thin cords can cause rope burns and injuries to people, children, dogs and other animals.
Good lead walking
It is a pleasure to walk a dog with good lead walking skills. Loose lead walking, positively trained recall and clear handling are more useful than an extendable lead.