Every app can have iCloud associated data that would be deleted when you uninstall the app. Also push notifications go through Apple’s servers and then Apple bundles them for different apps. Apple would need to know not to send push notifications to an app that is no longer installed.
Also of course Apple keeps a record of installed apps. If you drop your phone in the ocean and go to the Apple Store to buy a new one, your installed apps are reinstalled.
iCloud is the problem, here. Apple has no right to predecate my software usage on the existence of an account with them. It's equally as absurd as Windows requiring a Microsoft ID to log in.
Apple for over 40 years has sold integrated software and hardware and for over 20 has sold hardware + integrated online services (iPod+ iTunes) and now you are shocked that when you buy an Apple device you also buy into their ecosystem?
Exactly how is anything on the iPhone suppose to work without an account? Push notifications?
Most Android apps are also dependent on Google services and a Google account.
It's a package manager and tracker designed in such a way that it only talks to Apple's backend.
It's still the system package manager though.