Sure but then the well dries up for software maintenance and you end up with a slowly degrading product as the environment in which it runs slowly shifts around it.

Then you have to secure a new vendor when it eventually breaks completely which is basically the same as buying yearly versions. Or you pay a subscription/maintenance contract so that the software keeps being maintained.

The problem with software maintenance is that it isn't a 'full company' job so you have devs sitting around who might as well add features for large clients since it makes them happy and you keep getting that sweet ARR.