Austin, you might enjoy the article I posted - it gets into some detail about proactive things that adults can do for kids in these situations, different developmental stages of relationships, etc.
Kind of spells out the 'why this happens' part in ways I hadn't thought of (kids who don't easily connect, not much about kids who do easily connect, which I know is what started this thread!

)
The author breaks the kids into three groups. Its starts to get at why kids need a different set of services.
"The highly gifted child having peer difficulties because he or she is advanced over age peers in expectations for reciprocity and mutuality, in moral development and in specific needs for close intimate friends, needs contact with older gifted peers at similar levels of social development no matter what his or her age.
Even in preschool years many highly gifted children are ready for best friends and yearn for that closeness and intimacy. These children cannot be happy in a typical preschool class where friendships change daily based on activity needs."