As a developer in a professional context you'll hardly ever work alone or be the sole contributor.
Even if you use a GitHub profile just as your personal code repository code still is communication, even if it's just with your future self.
Therefore communication skills are crucial. A well-thought-out README file and consistent, readable code help others to understand your work. These aspects often are more important than what the code accomplishes.
Working, even efficient, but unmaintainable code is a risk. Ultimately, code is a precise specification of what the software at hand is supposed to do. If that specification is hard to understand it'll be much less useful.
