My experience with the iOS App Store has been that if you only just now heard of the app and your phone's too old, you can't even download the version that works for your phone.
That is what ends up forcing an upgrade. That people's phones can't run the newest version of an app, and aren't allowed to get an old version as a substitute.
We have a Ring with the app installed on an old phone that we use as the "household" phone. I was going to "upgrade" the household phone to be an old tablet which while newer and running a later version of Android, is still old. Can't install the Ring app on the newer tablet because it is too old. So we are stuck with the even older phone unless we buy something new.
Of course it's a viable solution only for an archivist/advanced users, not so for common users who just wish to keep their old device running smoothly.
The effect may be indirect - someone in a poor country with a 6 year old iDevice finds it becomes unusable, so they want to buy a 3 year old iDevice... And they're buying that from someone who has a 3 year old iDevice who sees that for not a lot of extra money they can buy the newest one.