Partly because a huge majority of firefighters in the USA are volunteers with donated equipment. Fires are rare enough outside cities that going on a call once or twice a week isn't that hard. If you're living in an area with a volunteer fire department you should consider signing up! Most of the volunteers in my company are under 18 or over 65. We desperately need healthy adults who can show up to a 30 minute call maybe once a week. You don't have to be in great shape as a volunteer, and you can refuse any order from command if you don't feel safe. I've thoroughly enjoyed being a volunteer.
Also we're building out a new socialized ambulance program that does add a small annual fee to all properties in the region to pay for the ambulance staff. We do also have volunteer EMTs, but the call load is much much higher. Not many EMT volunteers with other full time jobs want to wake up 10 times a night to drive Mrs. Soffia to the emergency room because her tummy hurts again. Paid staff on an ambulance crew actually makes a lot of logistical sense given how busy we are. We're very excited about it, the townships all voted to approve, so we're starting up in Jan 2027!