Because small towns in the US are dying. Manufacturing and ag are down, services and tech are up. The former provided jobs evenly spread throughout the US where raw materials and good land were. The latter encourage consolidation in denser metro areas.
A local government is an economic entity too. It takes in income from some set of people and distributes services in return. Taxes mean getting income from the residents, which in turn means those residents need to be acquiring money from outside of the area to compensate for that. When jobs are dying, that money stops coming in. Traffic fines let a small town extract money directly from people outside of the city, which means it places no burden on the citizens receiving the services.
I'm not saying this is morally justified, but that's how the system works economically.
These small towns are in a really rough spot. Many services are not fully elastic and can't arbitrarily scale down. It's not like you can say "the fire department only puts out fires between 3 and 6 PM." A sewer line that only goes halfway to a house is not 50% useful. Below a certain level of wealth and density, a city simply can't sustain the services it needs to provide to its citizens. Their options are:
1. Take in money from larger government organizations. State and federal funding can keep these cities alive. This is how, for example, they're able to still provide mail service, because it's the US Postal Service. With this, basically the larger metro areas are supporting these small towns out of duty to the greater good.
2. Extract money from people living outside of the area directly. That's what this article is about.
3. Disincorporate entirely. This does happen sometimes, but obviously this has a lot of downsides. Actual humans do live in these places, and these cities have long histories. Times change and some things do naturally go away, but there is a material loss when it happens.