Me too but here's one useful function:

Perhaps you are aware there is an ongoing event, say for example a football game, or an election, or an outage of your email service provider. You go to one of these "scream into the void" social sites, search on the topic, and learn what people are saying about it. Maybe someone knows what's really going on, maybe some of those people have some interesting insights and you engage with them, not unlike you and I are engaging right now. Others can observe, perhaps contribute, and after the event has concluded, everyone goes their own way. Hopefully in the end the interactions are beneficial for all.