A Question for Parents

I don't have kids so can parents explain to me why the hell some parents let their children grab like 10 -15 books and not have them put any back? Instead of working I have to stand guard so parents know they have to watch their children. But once I leave forgetaboutit crap is every where. If you bring your child to storytime on a regular basis either buy a book every once in a while or don't let your child trash the section. Today, I had a man come in with three kids, I assume they weren't his because the kids did whatever they wanted. I saw the three kids ten minutes before I saw the man, the oldest was maybe 6. They were yelling downstairs and riding the escalator up. I was joking with my co worker about calling DFACS. Right when I am about to tell them to stop the man appears. He takes the very loud three back to kids section. I go back that way and the three kids are trying to jump over a sitting stool with a running jump mind you. I am like wtf, really. I know the very loud three didn't go to church today. Anyhow I tell them there is no jumping over furniture in my way down deep you better listen to me voice. ( I didn't even know I had that voice). And then I hear the man behind me say see kids you can't do that. When I heard the man speak I was pissed. He was watching the kids do what they're not suppose to but said nothing its not my job to parent.