It may not be rocket science, but it's not 3rd grade math either. It's very likely that the house/land in question was worth much less than $100,000. If that was the fee, they couldn't have or wouldn't have paid it.
To answer your question, it appears that the people of the rural county that this man lived in did not in fact have any form of social responsibility or compassion. The government in that area, which was presumably expressing the will of its constituents, had apparently decided not to arrange for fire protection for all of the people outside the city who could be served by the city fire department. The people had decided to to leave it up to each individual as to whether or not to get the protection. The City had, after seeing that the owner of the house had not paid the fee, called him and written him a letter. For whatever reason, even after those communications where he was told what the consequences would be if he didn't pay and his house caught on fire, did not pay. It is sad, indeed, that this man subjected his family and pets to the consequences of his inaction.
Many people decide not to live in cities because they don't like to pay higher taxes for things like city water, city sewer, fire protection, city garbage collection, city building codes and inspections, etc. They also don't want to have to play by the rules that go along with city life. It's a choice -- you get what you pay for.