Somewhat to my surprise, I've found that at least 90% of candidates who include a GitHub username, when I go look at their repositories, either have nothing but unmodified forks of existing open-source projects or obvious "go through the tutorial for technology X" projects. I can totally get how, after seeing that kind of thing ten times in a row, people might give up looking.
But I still always look, both at the person's public repositories and at their contribution history in other public repos.