While there are some benefits to using the built-in parental control features in iOS, many are either too restrictive or do not cover the needs of most parents. You have no way to control internet access by a schedule for instance. Blocking the internet remotely is impossible using built-in functions. Most changes need to made while having physical access to the device. Also, making a decision on various categories or specific apps, especially remotely, is not possible. See this article here on iOS parental controls standard on iOS.