The US Navy was paying $9M to keep Windows XP updated and patched just for them.[0]
I bet if you pay Apple similar amounts of money per year, they'll keep specific APIs available just for you.
And it's not like updating the app to a new iOS version is a massive undertaking, in most cases it's just a matter of opening the project in XCode, adjusting the OS version, compiling and publishing it again.
I can't speak about iOS, but when I open Steam on macOS, I see more than 2/3 of my library unavailable since macOS Catalina, which entirely ruined macOS for gaming for me. Clearly, updating those wasn't so simple.
And also, it's unreasonable to expect all software projects to need updates, forever. My hammer doesn't need updates.
I bet if you pay Apple similar amounts of money per year, they'll keep specific APIs available just for you.
And it's not like updating the app to a new iOS version is a massive undertaking, in most cases it's just a matter of opening the project in XCode, adjusting the OS version, compiling and publishing it again.
[0] https://money.cnn.com/2015/06/26/technology/microsoft-window...