Unfortunately, the latest model is where the users are who habitually spend money on new stuff and are likely to pay you for anything.
If you're optimizing for money, rather than good use of system resources, it makes perfect sense.
The underlying platform purveyors unfortunately have the same view, which means that anything before the model before the current model is not supported any more. It probably has an outdated version of the OS. The current OS won't fit. The APIs are changing, and so supporting the old device requires maintaining a separate stream of the code that is backported. Someone has to test it on the old device and OS. And for what? Someone who won't pay.
If you're optimizing for money, rather than good use of system resources, it makes perfect sense.
The underlying platform purveyors unfortunately have the same view, which means that anything before the model before the current model is not supported any more. It probably has an outdated version of the OS. The current OS won't fit. The APIs are changing, and so supporting the old device requires maintaining a separate stream of the code that is backported. Someone has to test it on the old device and OS. And for what? Someone who won't pay.