Social Media Keeps You In Touch With Old Friends
In Your Twenties: You use social media to show the world what you're doing. Your friends are mostly current, with the exception of maybe people you used to know in school.

In Your Thirties: You're doing less showing and more watching what other people post. It's a nice way to know who is going to have a baby or finally got married or... You use it as a tool to see how old friends are doing and to network but it's not as important to your social life anymore. In fact, you often think about deleting it altogether.