It’s same as asking why should government control abuse of meth and heroin. These drugs along with social media, exploit certain nature of how our brain works to make us addicted and alter our state of mind.
I get your point is to have some more regulation, however the argument is much more nuanced than "Ban All Social Media" which is what I'm trying to portray.
We need high regulation of recommended content, probably by moving recommendations out of the scope of section 230. Pointing to a not banned but extremely highly regulated decriminalized sector kind of speaks for itself. It's not like I could go on a San Francisco street corner tomorrow and start selling pot like a paperboy.