That is the justification, yes. And it is impossible to tell whether there is a kid, an adult or a dog on my side of the tcp connection without mass internet surveillance which is the actual reason.
Won't someone think of the smartphone addicted adults!
You don't need mass internet surveillance. You can simply restrict advertisement much further than today: the types of things that can be advertised, where they can be advertised, etc. We restrict all sorts of harmful activities, why not extend it to ads?