I'm not in favor of these social media bans, but I would think the benefit here is that without the ban your child will be in the "real world" while everybody else's is on social media. This would make the "real world" socialization benefits more difficult.
I want my child to go out, but first I need to force every other child to go out. Maybe that's why children are not out? Because parents wait for all the other children to go out?
I mean, we view social networks as having network effects that keep people there. The same force that stops people from switching from Facebook and TikTok prevents people from abandoning social media altogether. Waiting for all the adults to be responsible and forward thinking seems a little far fetched.
So instead you are going to use the force of the state to tell them what they should do instead and then threaten them with violence/fines/jail time if they don't want to?