Sorry for that empty affirmation.
The reason to not use sites like Transifex or Crowdin is because it is difficult or almost impossible to track minor changes or updates the files, that is something common when translating sites, documentation or config files are updated everyday.
On that sites you have to convert the original files to their format, maybe a JSON file or another custom config file, and then convert it again to the real format used in the project.
Github make it easier to discuss about merge requests, commits or whatever another reason to discuss
Another reason are the contributors, is easy to track on Github the contributors list, something that developers value about his work.
And the final one, is Git after all, track all your changes 🙂
