Earlier quoted context omitted.
I find this comment really interesting, because NONE of my clients in the last 10 years of (self-) employment had even a single codebase on GitHub. I am contributing to a few open source projects on GitHub here and there though.
GitHub is not Git. Git is by far the most widely used VCS. The majority of code hosting services use it.
My clients don't use GitHub.
Most of my clients do use Git. (some use other VCS)
What made you think I thought differently?