How do you work in software for years and not find some little hole you want to fill
That's not the right conclusion to make. There are lots of developers who code in their spare time, but don't make their code public on Github.
I have had several side projects, but I am not inclined to share my code on Github. Either because I intend to make money off them, or because I don't have time to manage an open source project. Part of it is also caused by "imposter syndrome", where I don't have time to make the code good enough for public view.
You have over 200 public repos, which means you have a different view. But that doesn't mean that your coworkers don't do things on their spare time.
To be honest, I feel this attitude is beginning to spread to potential employers. Now we are expected to publish and be rated on our public repos, and it will just lead to lots of burned out developers in a few years that feel pressured to publish OSS and practice leetcode.