KM i can still technically set minimum version to iOS 12 (here's an example of someone else's app i found that launched this year with 12.0 minimum version) but the issue is a lot of popular frameworks devs use already force minimum versions
in addition to that, one of the biggest flaws with iOS itself is tying the browser version to the OS version. if your app has any screens or links to any pages that are powered by certain 2020s era web frameworks, they basically can only run on iOS 14/15 and up. whereas on android, Android 5 got browser updates all the way to 2021 and can actually run those same modern websites that can't even load on iOS 13. i ran into this issue myself and had to set my minimum version to 14.0 for the time being
(for example, sure, my iPad mini 2 technically got 6 years of software updates from iOS 7 to iOS 12. on the other hand, my 1st gen Moto G i bought for $80 the same year only got 1 update from Android 4 to 5.
yet, in reality, my iPad is next to useless now as it's forever stuck on a 2018 browser version. many pages simply appear as a white screen. meanwhile, my Moto G stuck on a 2014 Android version can still load and interact with modern websites through a 2021 version of Chrome although obviously it's very slow)
also, anyone who wants to use SwiftUI instead of UIKit on iOS (i.e. they might have hired devs who only know SwiftUI) or wants to use a SwiftUI library is already locked to at least iOS 15 or later in order to get most functionality
(Note that the Swift programming language itself technically supports all the way back to iOS 8, but then you'd only be able to write UIKit code with it. Swift*UI* is a more modern UI framework with a bunch of time-saving features like "live updating previews without needing to recompile" that launched with iOS 13. However, it didn't have enough features to actually be stable enough to use until 15ish. That's when it started becoming super popular. Outside of SwiftUI, I'm pretty sure Apple's current "enforced" minimum version for UIKit apps is iOS 12, same with any web-powered apps as long as they are built to still load on a non-updated 2018/2019 version of WebKit)
meanwhile, android's close equivalent to SwiftUI, Jetpack Compose (which is written in Kotlin, and is meant to replace a previous framework that used Java and XML), supports all the way back to Android 5. this is because any missing Jetpack Compose functionality gets bundled with the app, vs. iOS where an app needs to rely on the OS itself to provide all the neccessary SwiftUI functionality