This is exactly why Github will not ever be the standard. It's fine to show off what you play around with in your spare time, but the very best and most productive workers actually won't have an extensive up-to-date Github repo. This is because they're been gainfully employed and have spent the vast majority of their coding time kicking ass at their real job.

In short, while people with impressive Github contributions can generally be good employees (but not always!), many good employees simply don't have time or interest for open source / side projects.