I think parent means working on open source tasks is often "thankless" in the sense that it's extra work that doesn't necessarily benefit their employer.
That makes very little sense. They have use for it because it results in new features which are contributing to their business which would otherwise be both built and QCd by employees
Some things align w internal priorities and get done, others are issues FB people have not run into and they ask for contributions from whoever is affected.
In my experience, it's a fairly common theme in projects like jest or yarn.
If that entails working on OSS tasks on your personal time at the expense of spending time w/ family/friends (because you can't justify spending company time on it to your boss), I'd say a lot of people would choose to not "benefit society" / pamper demanding freeloaders / whatever you wanna call it.
I fully understand why people would choose not to work for free. But that was not the question. Work that does not benefit your employer tends to be work that your employer does not pay you for, but they're not the same.