1. They care enough to have a Github profile
2. I can see their actual interests.
3. I know they're interested in random experiments
4. I can see if and how they treat their projects. Are they dedicated maintainers, or do they just fire off one-shot projects without ever deciding to maintain them?
And a whole lot more. A person who maintains a single shell script project with diligence is worth more to me than a thousand developers with bullshit lisp and haskell repositories.
Yes, there's a bunch of great engineers with empty or bad github profiles out there. But those engineers aren't showing me that they're great engineers. The ones with a single or few well-maintained projects do.