There are a couple that aren't against it, but to actually implement age controls in the way they are being bought in you basically need to be an authoritarian. Otherwise, you'd be persuaded by arguments like Mullvad's that the social media companies already know how old their users are and don't need a centralised authority to tell them. There are alternatives here that are less authoritarian. Policy makers and the people supporting them don't want to use those approaches, because they support taking a more authoritarian approach.

These policies, in practice, are literally authoritarian policy. It isn't the most extreme form of it, but it isn't authoritarianism because I don't like it. I don't like it because, objectively, this is authoritarianism and authoritarianism tends not to work. Otherwise all the research I've seen suggests that kids shouldn't be using social media. If this wasn't likely to take out huge chunks of the healthy political dialog on the way it'd probably be tolerable.

If it is manipulation to point out that this is part of a class of strategies that have a history of horrible failures, then you have a very confused understanding of what manipulation is. This is an absolutely classic authoritarian "we can't just let people talk to each other however they like without the authorities being involved" play.