But at what age do you think this stops becoming an issue? 12? 14? 16? Older? Do you not think that Dad is going to bulldoze his way upstream, “flinging people back into there (sp) seats” for his 12 year old? Or his 14 year old? Or his 16 year old daughter? Where does it end?

No parent is going to leave a burning plane if one of their children is in that plane regardless of whether the child is 6 or 20. So your rationale is ridiculous. In your world, to prevent what you are using as the reason for seating parents and children together, ALL parents should be seated next to their kids, not just younger ones. So if your reasoning is truly this, then any parent travelling with any child should get free seating.