In some cases, some kids are much more... high maintainence than others. When I was a kid, apparently when my parents took me to a pier, I took off in an unpredictable instant and nearly ran right off into the water; luckily my dad caught me right in time-- hearing that, I would have thanked them if they put me on a leash as a kid. Fortunately, I didn't have too many experiences like that, but plenty of little children are bound to.
It can be a life-saver, not shackling.