Because advertising (and in particular targeted advertising) is so entrenched in every aspect of our lives and society that it's very hard to admit that it's harmful. Because doing so means admitting a multi-decade failure gross failure of the government and regulators, and accepting that we need a massive structural overhaul of the entire industry, and of the operating model of a significant chunk of the Internet.

Our aspirations for our children reflect our own anxieties. It's the same with social media bans.

Our culture is pretty permissive of businesses inflicting indirect harms on adults. I think a lot of that goes back to lobbying from the cigarette and alcohol industries.

Because the development and ability of minors to push back against adults is poor, and the ability to push back against corporations is abysmal.

If this works for kids, and then adults want it, it can then be considered.

Kids are more vulnerable

It's easier to sell when you can say "think of the children! they need to be protected" and then later extend it.

Constant surveillance has become the default order of things. Doing what's best for corporations is the default order of things. On the flip side, "think of the children" is a strong appeal to lawmakers and has won this round. Us adults still have to suffer under the thumb of big business though.