[Gud]

Why would it no longer be profitable to advertise to teens on YouTube just because they can’t have accounts?

[mathiaspoint]

Right they'll still have a persistent session that accumulates data for them. Just without the ability to persistent settings, subscriptions etc.

[azemetre]

Putting YouTube in the social media ban also removes personalized ads for teenagers. Personalized ad buys are very profitable for companies like Google and Meta. Hurting their ability to make money would only be a net positive for humanity.