Ask HN: Why Google does not love GitHub?

Why google search is not loving GitHub as mush as StackOverflow?. It already has the metrics to decide which github projects are popular and relevant and which are not. The latest evidence is I have searched for "email_spec gem". It lists the h-lame fork as the top one instaed of the original bmabey one. Why google is ignoring the releveant data like number of people watching the project and the number of forks for the project.

This is not a solitary case. I have a strong feeling that Google is at least not giving proper importance to GitHub projects. Thoughts?