What if you are walking down the street and a cat runs across the road? I had a cat run across the road this morning as I pulled into my driveway. Luke spotted it right away so when I lifted the back hatch I gave him a very firm "wait." I grabbed his harness and held tight until we got into the house. Luke is very well trained but in a moment of elevated prey drive he could easily forget and bolt. Once your dog is hit by a car it is too late to change your mind, too late to put the leash on just in case. So what I say is the point?
Yes I work my dogs off leash, Luke that is and in a park setting. He is very good even with distractions but why would I risk the chance of him being injured? There is no point, he is going to be walking beside me anyway so why not have a safety line between us? Working off leash is essential; you don't want to have to have a leash on to control your dog. But working safely off leash and just off leash wherever are two different things. I'm not a big leash fan but they are wonderful for keeping dogs safe.
Off leash work is great and it is a terrific feeling having a dog so well trained. But; never do it on a street, road, lane, path or blvd that has moving vehicles or is even near moving vehicles. That's just plain common sense, never the less people do it and dogs are injured or worse. A leash can save a dogs life.