1) E.C.s coupled with high gpa shows that you're smart/efficient in time management/and can handle both the academia and "outside interests" at the same time. Compare this to the guy who studies 15 hours a day, and gets a 4.0. What happens when the course load increases? There won't be enough time in one day to study at that rate and depth.
2) "The Universe tends to unfold the way it should." ~ Black Guy In Jail from Harold and Kumar Go To White Castle
I think that those who are more interested in caring for patients, and are more philanthropic will go into primary care whereas those who are very competitive and want the prestige/money/etc will go into the more competitive residencies which often involve less patient to doctor interaction and more physical work. So for the most part, you're not really going to see as many socially adept/apathetic doctors in general practice versus the more competitive residencies.