No, not every phone and computer has parental control options. What about the PCs at libraries and schools? What about older siblings? Other students? Friends of the kid? It's completely unrealistic to claim parents should just supervise every media usage.
People also aren't robots where you put "upbringing" in and get predictable results. You can teach them all you want, unless you completely ignore all privacy rights of your children, you won't be able to control their media consumption.