Erm, it's a paid upgrade per major release, which may happen every year. The old version still works, you don't have to upgrade. Just because Apple moved to give OS updates for free, doesn't mean every software house has to become a charity too.
Back in the day, Software developers sold via retail shops (harder to reach customers on the opposite of a download link) yet they were sustainable and profitable. AFAIK, only big releases were to paid for which were like a new software not an update.
Now they claim they need to releases yearly updates (mostly same software) to keep on going although user base is much larger (I am sure more people use computers today than 1998). Its fine, but the developer has to understand the consumer does not have infinite pocket either. You pay yearly for VMWare, Apple Music, Netflix, Microsoft Office, Adobe Suite, 1password, Cloud Sotrage... you see where I am going with this.
1 time pay is fine, yearly is a bad business model due to consumer pocket limits. I think 3-5 years upgrade cycle is more acceptable.
HOW DARE THEY OFFER SIGNIFICANT UPDATES WHICH REQUIRE TONS OF WORK AND RESOURCES AND EXPECT TO BE PAID FOR IT!
I'm sure you work for free at your job.
Due to the nature of the internet business model, the developer can code once and sell many times. Ex... they write the software once and sell 1M copies. Thats $79M in this case. It should last them a nice while. You basically continue to make more money but not doing more work as more people opt for your software.
You also have the advantage of writing a little bit more code and releases it as "NEW" upgrade for the same price you sold it when you started from scratch.
Compare that to a car mechanic which can only fix 1 car at a time, and will get paid for fixing each car on its own.