I find it rewarding to volunteer at one of the big open source software foundations because the time I put in working on project governance, licensing, policy and so on ripples out through hundreds of projects and into the broader FOSS ecosystem. We're way better at what we do than we were even a few years ago, and one result is that there are far more people getting paid to work on FOSS.

Expertise on the administrative aspects of open source also makes me more valuable as an employee, because I can help my employer to consume and contribute to FOSS safely and efficiently. I recommend that anyone with the knack get involved.