I think the assumption is, at least from mine and others like me, is that if your dog is off-leash, you can handle your dog off-leash. The same if you bring friends to some social event, you wouldn't bring them if you can't handle them and they can behave in public. I'm not afraid they are gonna attack me, although sometimes humans do attack other humans, most of them are fine so no need to worry in general.
> but where I’m from we have a scourge of ignorant owners who are not in control of their dogs. They ruin it for everybody.
Yes, I agree, it's terrible when owners have no control over their dogs. But that's not relevant to the leash itself, that's relevant to the expertise of the owner. Dogs on leashes misbehave as well, and can easily (if wanted and the owner is a terrible one) unleash themselves by either raw power or the owner not paying attention.