There are a lot of things parents can do on their own, but their mental capacity is limited, and things like this make it easier. Peer pressure exists, this helps level the playing field. It also makes it availible to all parents, regardless of how they get their internet (not always a home router).
I can also always stop my kid from looking at advertisements targeted directly at kids as a parent. But it's a lot fucking easier in Québec where it's banned and I didn't have to deal with cartoons of cereal boxes.