Why is it that we need human relationships?
There are plenty of animals that stake out on their own, relying on nothing for their survival.
And then there are insects who's sole purpose is to serve their queen.

But us? We're not either of those.

Humans are a separate breed when you consider our motivation in life.
Anything that you do in life is based on desire correct?
Money, fame, family. They're things that you desire.
Now connect back and start thinking even more.
Say I desire money. Why?
Maybe it's to support my family, or maybe it's to start a new business.
Why do i want to do that?

Biologists would say, "It's because of your survival instinct"

But we're beings who've developed over a few millennium. Our instincts must have diminished from that of our forestry ancestors shouldn't they?
Then what is it that drives us forward?

Take a situation where you want money for your family.
Why?
You want to provide better things for them.
Why?
To keep them happy.

At this point of the ride, you might say "Other's happiness is my happiness"
Sorry, but that only works in movies and cheesy relationships.

So why do you want to keep them happy?
Because it raises their opinion of you.
And why would you want that?

Because after you strip away all that complexity from your brain, the last thing that you'd find would be that it desires acceptance.

Why do we outcasts of society kill themselves every other day? Shouldn't this 'survival instinct' of theirs be strong enough to stop them?
It doesn't happen because in the depths of our mind, acceptance is what we crave the most. We want to be accepted into our community, into our circle of friends, into our family.
Acceptance is what our life is based upon.

Put a human being alone on a planet. He'll kill himself. Why? Not because he thinks he has no purpose but rather because he doesn't have other people to tell him that he does.
In cases like these that really push the human mind, you'll find that our 'survival' instinct is just some rudimentary tool that we've dulled down generation after generation.

So where do human relationships come into all of this?

Someone's opinion of you relates to their acceptance. To get someone else's opinion you need to know them right? You need to be in some sort of acquaintanceship.

There we go. That's why we need relationships.
Humans are social driven creatures, but we're different from other animals that act that same because our desire is much higher. And why is it so?

Because we crave acceptance.

You may deny it. You may tell me that I'm spewing nonsense right now. But think closely and tell me if your biggest problems haven't always been related to people you know, people who had a bad opinion of you, people who didn't accept you.

There's a philosophical principle called the 'Anthropic principle' that tells you that the reason the universe exists is because we're here to observe it.

The same way, I say, the reason our life exists, the reason we do the things we do, the reason we have goals and strive to achieve them, is all because there's someone we know who's observing us all the time and all that we want from them is their acceptance.