Exactly, since to you believe a local airport is managed the same as local parks, libraries, fire departments, etc. So what percentage of the local "public good" directly benefit from a local airport?
And if you look closely enough at the data, you'll find a number of those local airports that have the potential to grow are making moves for greater autonomy from those local governments for those exact same reasons. Unfortunately, as I noted above recreational Part 91 aircraft are not revenue generators like the commercial side of GA. Just follow what Signature has been doing. Regardless, on average 10 GA airports are closed every year, but not from a lack of need. Rather the collective local "public good" prefers their money spent on more libraries, fire stations, and even golf courses especially when you have a large open, former airport, to build one on.