I don't understand the purpose of being in a relationship. Is it just about having someone to talk to and vent with?

I've been single for about six years, and I’ve been reflecting on what relationships are really about. I watch shows like Married at First Sight, and I notice that in almost every scene, it’s the same thing—people asking each other questions, getting to know one another, talking about their feelings, and venting. It makes me wonder: is that the purpose of relationships? Having someone to talk to, vent to, and ask questions ? Or is there more to it than that?
I guess I just don’t get it, and I’m not sure if it’s because I’ve been on my own for so long.