In the most literal sense you're absolutely right of course. You can live without them. However, the real world isn't doesn't work on such absolutes.

Social isolation and loneliness are dibilitating conditions that can lead to serious mental illness (depression, anxiety, etc), so if you're not in a position to socialise without at least Facebook or a smartphone you should think twice before cancelling them. Many, many people would find themselves left out of group events if they cancelled their social media accounts. It's the de facto way of organising things these days. That is something that's well worth thinking about before making the leap.

I've spent long periods of my life working from remote locations, and without an internet connection to talk to my friends it would have (figuratively) killed me.