They actually do that?

Today i was walking back from the tube station and i seen a little kid on a LEASH!
Ive heard about these child leashes but never experienced it with my own two eyes. I dont really know the purpose of it, i guess to keep an eye on your children so they dont run away?? If so just hold their hand. I feel like they are treating the child as if they are a pet. What do you teach your kids when you put them on a leash? I had so many questions for the parent.
Is that good or bad parenting? Like if you need your kid on a leash than you must cant control your child any other way. They must not listen to your words for you to have them on a leash. I dont know man but that was weird, felt sorry for the little girl actually