Why do people say some music "inappropriate for children"?

That's what my parents tell me. I don't understand it either. Music is music. It's entertainment which can turn into an activity. I think it is because most parents are too over-protective of their children & don't want them to get into drugs, alcohol, and from listening to music. (Which makes absolutely NO sense at all) Yes, I want to be a famous singer, mostly everyone does. But, I'm not going to do drugs, drink, & have to be able to do all of those things like the famous rappers out there such as Wiz Khalifa & Lil Wayne. (No bad comments, I love both of them) It's all common sense that adults forget that kids also have when their younger & not only when they grow up. We also know that those things are bad and we should stay away from them.