Subscriptions only make sense for apps which you are using on a regular basis and where you would expect frequent updates or a regular service provided by the app developer. I am not willing to pay regular subscriptions for an app, which I might not use for a longer period of time. With upgrade pricing, you can decide whether you want new features/maintenance, or just keep continue to use the old application. Which is especially important with respect to your data. With a subscription model you might effectively loose access to your data once the subscription runs out. With the paid upgrade model, you retain access to your data, even if you don't regularly use your app.
It is another problem of the Apple universe, that applications often stops working some time after no update, because Apple keeps breaking old applications. This is one reason which locks me out of Catalina.