Why would an airline have any business in acquiring, getting approved/zoned, and constructing an bespoke airport close to a major metro that would presumably only benefit that airline? Airlines already operate at razor thin margins, specialize in only the transporting aspect, and would
not be the best party to oversee the development of airfields and airports. Additionally, companies other than the major airlines use an airport, from cargo carriers (large jetliners to “FedEx feeder”-type routes), private operations like NetJets, and even privately owned and operated aircraft all use it.
This is solidly the domain of a local company, collective, or a local municipality that understands this business and every aspect of it. Airlines are happy to pay usage fees (landing fees, gate fees, leasing) to specifically not deal with airport operations unrelated to their own fleet and operations.
We need to find ways to improve the process from initial concept, terminal layout, retail spaces, and public ground transport that connects to the city center.
Also, usually the airport is there before homes were built so every owner in the flight path made the decision to live there.