This is an unfair parallel, but it's like worrying about businesses who advertise on pornographic sites or on cigarette boxes. Allowing visibility to businesses who advertise on a certain platform could be judged (by society, law, and voters) to be outweighed by the need to restrict youth access to social media. There is a variety of precedent in society and law in restricting youth access to something that is otherwise deemed legal. Just because businesses advertise on social media (in my opinion), the decision to restrict access should not be altered by that advertising strategy.
Why is this even a problem?
Oh no, businesses can’t target advertising directly at children?