It's not just a question of money, but legal arrangements. Going into a fire isn't a game--it puts the firefighters and their equipment at risk. What does the firefighters' insurance contract look like? If one of the firefighters gets hurt, is their insurance going to cover it when the fire was outside the jurisdiction of that fire department? Insofar as this illustrates a "problem" it's not a "third-world" one, but a distinctly American one. Americans are the most legalistic people in the world, and reflexively accept the consequences of the legal state of affairs. In many other contexts, that's a strength, not a weakness.
> This whole "unincorporated land" execuse is a sad state of affairs. The whole "You're not with us, so it's not our problem" mindset is really why America is so low down on every single ranking in the world, except for military might.
Even Americans aren't so tribal as to hold grudges between towns and adjacent unincorporated land. The significance of the house being on unincorporated land is that it demarcates the legal boundaries of the fire department's jurisdiction. A public body acting outside its jurisdiction can have all sorts of consequences.