In practice, though, you need to upgrade to stay current. For software that people use as a daily driver, subscriptions are not obviously more expensive in general.
that's where we disagree: you don't usually need to stay current. as long as it does the job, it's current enough. if there's new features available that would add value to the business, then you have a business case to buy a new license. 95% of software update haven't really added any value since the early 00s.
I'm not sure I want to work at a company that nickels and dimes purchases to the degree that I'm running unsupported 20 year old software because someone in procurement doesn't think I need an upgrade unless I write up a business case for it. I assume they're equally cheap in many other ways.
So, in other words, you need to upgrade--or have a subscription. In fact, extended support agreements for some enterprise products are a premium offering that don't require moving up to the next version given the effort associated with backporting bug fixes for a fairly small base.
and that's why we ended up with agile and alpha crapware released every week, breaking functionality that used to work and moving everything useful around until you can't find it.