It baffles me that more countries haven't put legislation in place to severely limit what ads can be served to under 18 year olds (or at least under 16).
I worked in an ad agency a number of years ago, and Phillip Morris approached us with a deliberate plan to launch big budget ad campaigns on social media platforms specifically because they could get in front of younger demos more easily (traditional media having existing regulations in my country).
The original idea was to build a large database of prospects to sell direct to even after regulation eventually cracks down on them. Amazingly no regulation has come yet, and Meta has done little to no self-regulation.
You can blame parents, but even then one under appreciated problem with digital ads is the lack of shared experience. With TV advertising, you know what your kid is seeing, everyone can see a verify what ad ran at what time on what channel etc. If a parent and a kid are scrolling social media their experience is entirely different, and you can't go back and see what someone else has seen.
Probably because being tracked across all platforms is a bad idea in a democractic/liberal type of country, and not worth the "think of the children" argument. At some point parents have to take some responsibility.
My kid recently got a second hand iPad tablet. On it, she uses YouTube Kids. I made an account for her. Now, they ask _me_ for consent, since she cannot legally give it. They throw ads at her about toys, but this is illegal in my country to target children with ads. Ads are supposed to target parents, not kids. Now, if it were one ad at start, I'd hate it, but they go further: in a 10-minute movie, the thing quits like 3 times to show my kid an ad. She barely has the attention span to watch the bloody vid! You know why they do it? Not because it is legal; because they get away with it. Law is irrelevant if it isn't uphold.