Social media addiction would have the same problem as any sort of addiction really: it prevents you from carrying out a normal life via distracting you from everything else that's important for you to do.
But there's two questions that need to be asked first:
1) What is the official medical definition of addiction?
2) Do these people actually meet this definition and could in fact be diagnosed with an addiction problem?
Because it's possible that the people who are being claimed to be addicted to social media might not actually be, much in the same way that people claim to have OCD or ADD (and the number of other conditions people claim to have) but don't really have Obsessive Compulsive Disorder or Attention Deficit Disorder (or the other conditions they might claim to have). If it's this and not legitimate addiction....well, you just have no self-control and need to work on that. Or that's just how you spend your free time. If it's legitimate addiction, then people should be given proper medical treatment.
Who is making the claim anyway that people are addicted to social media, and what do they have to back this claim up? Cuz I kiiiiiiiiiiinda think it's just people who don't like how prevalent social media is these days cuz it's not how they're used to the world. Social media is just the new norm of society, much like how television became a completely normal and commonplace part of life years ago.