Ever stop to think about how much of American society is built around the immediate family? It's kind of weird when you compare it to the way human beings have lived for majority of our history.
As a hunter gatherer society, our natural state of being, we used to travel across great distances with the same group of 100-200 people, sharing resources and duties as a common collective. All adults looked over all children, no one profited while another suffered, and we had an intimate relationship with our environment, being fully embedded in it and reliant on it for our survival. Look how far we've come. We've rearranged our routines and lifestyles to match the nuclear family, creating this really weird disconnected society. Each family lives in it's box, surrounded by empty roads and other boxes lived in by strangers who we have no deep ties to. And miles away our close friends and other family members live in their own small boxes surrounded by strangers and empty roads. Thank god we have small boxes to transport us from one box to another box in order to see the people we love right! We get our food from another box, having no connection to the earth where it grew, and the resources it took to grow it. Everything has been whittled down to these economic processes of efficiency, and in our focus on self-benefit, we've forgotten what gives our lives value beyond the basics, connection to something greater than ourselves.
Human beings are social creatures, and we are also flawed. Want to hear a tale of two cities? We live in the most connected yet disconnected society ever. We have great wealth, but are poor in spirit. We live in our heads because we don't know how to be ourselves, and this inability to interact on a deeper level limits our human experience. Our culture seems to be built on a foundation of self-doubt, leaving us unable to love our whole selves. We see and hear judgement everywhere, and fear that it may fall on us. Then when we get in a relationship we think that we've found the one person that we can drop our guard with, and be fully accepted by. That to me is the reason why so many people disappear when they get into a relationship; they think they've found the one stop shop to happiness. And it's bogus! That's so much pressure on one person, and it limits the quality of interactions we have with friends, and more importantly with strangers. If we think no one can understand us and are afraid to try, then no relationship will ever be healthy. We'll continue to be these disconnected husks that fail to find what we're truly looking for, a life of love and acceptance.
Let's face it, we can't spend every waking moment with one person and still be happy, we still have to interact with the rest of the world on some level. I advocate for real moments of sincerity and honesty with as many people as possible, even if it is TMI or uncomfortable. Pushing the boundaries of acceptable human interaction will evolve our understanding of relationships.
TL;DR - People rely way too much on romantic relationships for their intimacy needs.