Volunteering is good. It's good for your career. It's good for your soul. (Assuming you believe you have one.) It's good for your character. (Assuming you believe you don't have a soul.) It can get you badges. (Well, one badge, anyway.) Generally it's also good for other people, too.
I've always done volunteer work. My people were church people, so there's a lot of volunteering there. (As opposed to the military, where their motto is "Never volunteer.") I've always been on committees and boards and execs, and run conferences and events, but I also muck in with emergency management and disasters. (I also train, so I know how to muck in when disaster strikes. This comes back to that "Generally it's also good for other people" part: you do have to prepare so you know how.)
Some of it's formal, some volunteering isn't. As well as being on committees and stuff, for years I did reviews of antivirus software and, later, technical literature. I did it for free, and created (over some years) a fair resource that many people found useful.
(I got paid, some, for the books that I wrote, so, technically, I guess it wasn't volunteering. However, as anyone who has written a technical book will tell you, it's an awful lot of work for very little pay, so it comes close. I figure my first book paid me about sixteen cents an hour ...)
Yes, sometimes you get paid with money when you volunteer but mostly you get paid in experience and experiences. In addition to my volunteer work here, I volunteer as a coach. For the past 15 years I have put up with some pretty nasty situations and parents, but I have touched the lives of several kids. The trade-off is worth it. I have had kids come back year after year when, if truth be told, they wouldn't have returned based off of their skill level in sports. I have helped kids make lasting memories that they otherwise would not have had.
Volunteering has helped me achieve rapid growth in my career and it can for yours too.