The Economic Model of Relationships:

The Value of Others (Orion Taraban):

"People want things from other people. This is why other people represent both a potential solution and a potential problem. They are a potential solution when they have the things we want and are willing to give them to us. On the other hand, they are a potential problem when they don't have the things we want - or when they do have them but won't give them to us. And it's far from straightforward to determine which people are which - which is why other people are typically a problem until they prove otherwise."