Sorry that is not always the case. Some kids do have control problems and it does not always have to do with the parents. For instance, my daughter has a communication problem (which is getting better) due to what the doctors say is caused by low muscle tone in various parts of her throat, larynx, etc. Due to this she has extreme temper tantrums from the frustration she has from not getting her points across. We have gotten looks from some people when she has a melt down and you can see they are thinking we don’t know how to control our daughter. But they don’t have a clue, and I don’t really care if they do or not. They don’t know, so they should not judge.
Also, as mentioned by others it is easy for a child to disappear really fast if you just look away for a second. So unless you hold your child’s hand at all times, there is a chance they can slip away. The leash is much better alternative to that.
All this being said, I don’t put my child on a leash. I just don’t think people should judge a situation they have no clue about.