Ok, so I didn't read through every single response in this thread so forgive me if this has been stated already...
"Leashes" for children aren't meant to be cruel. They serve multiple purposes. Added protection is one, it makes it more difficult for someone to *bleep* your child while you're say, bending down to pick up your wallet you accidentally dropped. They prevent your child from wandering too far away and/or getting lost in a crowd.
Trying to keep up with a young, curious, adventurous (or rebellious) child while you're attempting to get say, grocery shopping done, isn't always the easiest of tasks whether your child listens well or not. Children get curious and often lose focus (or simply forget), therefore they wander off and/or want to go investigate a toy or candy machine, something of the like.
Using said "leashes" for children has nothing to do with being lazy. There are also parents, grandparents, other relatives, or guardians that simply cannot keep the same quick pace as a young child.
My last point is this: Have you ever dealt with a young child who has any form of autism? I have. We used a form of "leash" when she was young for all of my previous points. With a child like this, (who at the time we hadn't any idea of what exactly was wrong & why things were the way they were with her [attention issues, understanding/comprehension, ability to listen & do as told, etc.] and the fact that multiple doctors hadn't any clue what was wrong either) not only is it extremely difficult for the parents/relatives/etc. but also for the child. Does this make me a bad person? Does this mean we're lazy? No, it doesn't. This "leash" did a great deal of good of for all of us. So don't trash talk something (or people) just because you don't fully understand it (or them). There is nothing wrong with using a "leash" for your children, so long as it's being used properly. If you had been in my situation, all you nay-sayers would certainly be singing a different tune. Just sayin'.