Making new friends

Why is it that kids can make new friends in under a minute? No matter where they are, if they see a new little person about their age they will, with absolutely no hesitation, walk up to that person and proceed to say, “you want to play?”.
Of course, the general responds is a yes. The kids don’t look each other up and down. They don’t take a moment to think it over, or ask what their religious affiliation ism or even to look at the color of the other child’s skin. They just say yes and proceed to run off together and play.
Why can’t we all play together like children?