It is indeed weak, but organizations need a way to justify expense. Look back to the 80s and 90s; when two candidates applied for the same role the one with college degree go it. Even if the non-degree person had experience.
GitHub is a way for organizations to see you actually do something; other than BS your way through the interview process (which is also broken, but that's another topic).
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.