Exactly.
I get what imhotep397 is saying. I do. There IS a lot of time and effort going on here. The mere suggestion that these developers wouldn’t jump at a chance to get paid seems a little odd In this day and age. However, as shocking is the notion that altruism exists. People sometime do stuff for the greater good. They sacrifice their time, effort, and a bit of sanity so that others may benefit. An excellent example would be the moderation staff for sites such as this.
Having moderated large sites for nearly a decade, I know exactly how much of a task it can be. Without even trying too hard, it ends up being a second job. No pay. No thanks. Sleepless nights. 10 years doing the mod/admin thing as a volunteer. Would I have asked to get paid or accepted a check? Probably not. No. That’s not why I was doing it. You do it because you love the community and what it represents. You do it for others’ sake. You do it because, frankly, nobody else is stupid enough to. 
I suspect that there are numerous volunteer Blender developers who feel the same. This is about passion and a desire to contribute. It’s not about money. As we head toward 2020, that seems about as foreign a concept as any. However, some people donate their time and sweat to build houses, expecting nothing in return. Others wait on others in soup kitchens. Being a volunteer Blender developer is probably nowhere near as impactful as feeding or housing the homeless, but the drive and selflessness are still the same.