Because issuing a prohibition is basically always a punishment of the people to distract from who is actually causing the problem.

From a political standpoint it very much is either/or, this is done to exhaust any momentum towards systemic change.

“Ban the children to protect them” is an extremely shortsighted way to approach any policy or social ill. Kids will find a way to access social media, and this ban means they’ll need to do it in secret. So now anybody preying on them through those means has their implicit cooperation in covering up the abuse. That includes the media platforms themselves.

Also, why would you need to ban children from social media if the addictive strategies were under control?

A ban like this is only going to cause harm.