There are two kinds of people in the world—those who think there are two kinds of people, and those who don't.  But for the sake of the discussion, let's assume there are, in fact, two kinds of people.
Let’s say that the first group are givers. 
It follows then that the other group are takers. 

The givers are kind, generous, and care about other people, our environment, and our communities. 
The takers, however, are mostly interested in what they can get from any interaction.  They focus on how to take advantage of people, or perhaps they don't care how someone else does as long as they themselves are doing well.  They are narcissistic.  And they are people you cannot trust to have your best interests at heart. 

So let me ask you this:

Would you want to be raised by a parent who is a taker? 

Would you want your child to be a taker? 

Would you want your best friend to be a taker? 

Would you yourself want to be perceived as careless?  As selfish?  As untrusting and narcissistic?

The answers seems obvious.  You would always choose to be close to people who are givers.  We all care more about people who are generous.  And they in turn will benefit from your caring about them.

And all this means that people who are strong givers will more likely have richer, healthier, and happier lives.