Thing is, software unlike say a book or a movie has sometimes significant maintenance costs. There are always bugs to be fixed, security vulnerabilities are found, third-party libraries need to be upgraded and so on.

The danger of the one-off model is that it sometimes creates the wrong incentives. Features and even bug fixes get pushed into newer versions, which may even delay their release until there's enough of them to justify a new version.

A good example of this going awry is the RAW file processing for Photoshop (pre-subscription). Newer cameras would get added to new versions of the Camera Raw plugin but you needed a new version of Photoshop to use the newer Camera Raw versions.

I honestly don't mind the subscription model and I think Jetbrains has about the best one of all: you get constant acess to upgrades. When you choose to stop subscribing, that simply locks in the latest version you can use (ie you don't lose access entirely).

The problem is many companies price subscriptions wrong. They say "our software costs $600 so we should charge $50/month". Because, you know, recouping that cost in a year is somehow reasonable.