As a user, it did a lot to increase software quality: not just catching inadvertent bugs, but also ensuring that there was at least some reproducible way to get the code working, that didn't depend on some implicit configuration of the authors system.
As a maintainer, accepting simple pull requests becomes much easier when you can quickly look over the code and check the CI status, and not have to try it out locally yourself. It was certainly critical to the "social coding" idea behind GitHub.
So thanks to the team that put it together. Even if the product you built doesn't live on in the way you hoped, it has certainly had a lasting impact for the better on the open source world.