Because volunteers spend so much less of their time actually fighting fire. 70% of firefighters being volunteers doesn't mean anything like 70% of firefighting

Because volunteers spend so much less of their time actually fighting fire. 70% of firefighters being volunteers doesn't mean anything like 70% of firefighting is done by volunteers. And don't expect the volunteers to accomplish much--when the alarm goes off they have to go to the firehouse first, and thus will have a bad response time compared to a professional fire service. They're far more about keeping the fire from spreading than actually putting it out.