Cigarettes directly cause physical harm and even death. Social media can sometimes, under certain circumstances, depending on who exactly you're interacting with on social media, indirectly contribute to emotional harm.
Cigarettes are also physically addictive. Your body actually becomes dependent on them and will throw a fit if you try to stop using them. Social media is only "addictive" in the loose sense that all fun, mentally engaging activities are.
I'm not saying social media is fine for kids and we shouldn't do anything to reduce their use of it (TV and video games can be equally unhealthy IMO). I'm not even necessarily against legislation on the subject. But there's a huge difference between fining a company for breaking a law, and fining them for making a perfectly legal product "too fun" because you let your kids spend all their time on it and that turned out to be unhealthy.
This type of civil litigation where the courts effectively create and enforce ex post facto laws based on their opinion about whether perfectly reasonable, 100% legal actions indirectly contribute to bad outcomes is not a great aspect of our legal system IMO.
