The reason is that we let adults choose what to consume.
If you go down the path of banning social media feeds because they might be addictive, prepare for the floodgates of banning alcohol, porn, cigarettes, and more. Some people who don't consume any of those things will gleefully cheer this idea on, but I assure you there are people out there who would gladly ride this wave to start banning things you actually like, too.
Does anyone else find it weird to see so many comments on sites like Hacker News that are in favor of governments regulating what adults can consume? Years ago sites like HN and Slashdot were universally in agreement about internet freedoms, but now it's common to see people inviting government control of the internet for adults. I don't get it.