The majority of companies across the world don't have any repository on Github.

Github is for FOSS projects, or building CV portfolios for startups that think we don't have anything else to do after work.

I am yet to work for any customer that cares about git for example, so not even private repos.

So far my use of git has been on personal projects.

My anecdata is exactly the opposite: I have worked for four companies in the last 12 years, 2 big multinationals, mining and defence. All four used git.

Lots of large companies use git internally but they do not necessarily use github for hosting.

Gitlab self hosted is just one of many options.

Fortune 500 companies.

Quality is debatable.

> Quality is debatable.

Using a VCS is not though.

And sure, you didn't say they didn't, but using SVN or CVS in 2017 isn't good (outside of a very few select situations/industries).

Don't be proud of working for large, slow moving companies with poor tech choices. They don't use git yet but they will.

Don't forget mercurial: it's not used much for FOSS due to GitHub, but has a pretty strong hold in private companies. It's better than git (historically, not sure if it's still true in 2018) at dealing with Windows and huge repositories. And perforce for the truly humongous code bases...

The risk/reward ratio to leave svn/mercurial/CVS for git is generally pretty weak and a lot of really big companies started before git.

Sample bias. I suspect the vast majority of binaries in the wild were compiled with little, if any, code hosted on GitHub.