You’re conflating target version with minimum supported version.
There aren’t requirements to update the minimum. They’re independent. There might be limitations on what APIs are still available though in Xcode if they’re removed after a deprecation period however.
You can use the latest SDK, and if you don’t use any new APIs, your app will continue to deploy to whatever minimum you have set.
If you want to use the new APIs, you can put their use behind availability checks.
It’s just that at some point, as a dev, you want to stop testing on older devices and you want to stop branching your code for OS versions that are a minuscule fraction of the active user base. The ROI changes quickly.
I think a lot of people in this thread are mistaking SDK version and minimum supported version.
The App store requires you to link with a minimum SDK version, but the minimum supported version is set independently by the developer in Xcode. The latest version of Xcode + the latest SDK can still support devices running iOS 15. Developers are deliberately choosing to drop such support. Or maybe they just don't know how, as evidenced in this thread.
Xcode occasionally bumps the minimum will compile for without complaint.
Yes, but even with the current latest SDK and latest Xcode, iOS 15 can be set as the minimum supported version.
Which, importantly means you can support devices back to the iPhone 6S that is a decade old at this point.