It's why you can't install the same app that worked on your iPhone 8 when you bought it, today. It's the reason you can't install one that worked two years ago

It's why you can't install the same app that worked on your iPhone 8 when you bought it, today. It's the reason you can't install one that worked two years ago unless the developer is constantly keeping up with Apple's mercurial and inscrutable os-level API changes. Apple breaks APIs regularly and you're left hoping a dev wants to do free work to keep it working for people who already bought it. Edit: clarity