In a typical social situation, I think's it's similar to looking into a mirror in those moments when you recognize yourself as existing outside of your own head, but socializing is a much more profound experience. The other person has to mirror your body language and opinions (to a large extent) for it to work well and if it does, then you're left with a stronger sense of self as being of this world, rather than being alienated from it.
It's by no means the only way to experience whatever it is we're really looking for, so to speak, but socializing is well adapted to and encouraged by the system we live in. There's a very large industry that thrives on it which will push the narrative that you're not living life to the full by not taking part.
I'm saying this as somebody who doesn't take part, so I may be completely wrong.