Because as I clearly pointed out " forever licenses don't scale to keep a steady income per month after the user base is settled".
After a tipping point no one is buying new versions in an amount that can keep the salaries of the building rent, employees salaries, company taxes and whatever else is required monthly in a continuous flow that can keep the company going, without starting to cut down business costs.
The only new feature most will care about is that the version they own doesn't run on the new OS.
It is exactly the same thing as people stuck in Java 8, Python 2, .NET Framework, C99, C++11,... it works for the purposes of their employeer, and the costs to upgrade doesn't justify the outcome, unless forced by external factors.
Subscriptions started exactly because that model doesn't scale.
Anyone that starts a business quickly discovers how "easy" these things are in practice.