I’m not sure it’s that simple.
All of these except Minecraft have perpetual funding and labour issues, especially for the less sexy parts.
You’re not going to staff a pharmaceutical factory with volunteers.
Firefighting is probably one of the best fields to attract volunteers to. Save lives, glamorous, awesome PR, play with cool ‘toys’. Downside is danger but there’s enough people for whom that’s an upside.
Does that mean they’re all/mostly trainable, stick around long enough to justify the training, and willing to put in the work even when it comes to more mundane tasks like training, cleaning, equipment overhaul, drying pipes etc?
I believe most places have both paid and volunteer firefighters and I imagine it’s for a reason.
Downside is danger but there’s enough people for whom that’s an upside.
Worth noting that the shit firefighters breath in absolutely will shave years off their lives.
There’s a growing body of evidence that the payouts from the 9/11 first responders funds are for medical care that’s not exclusive to first responders to 9/11 specifically but just normal long term effects of being a first responder to fires and disasters in general.