It does appear to be an actual business practice. I have a 2006 Mac Pro which was running Parallels 9 flawlessly, and that was great because the computer is going out of date but is still great because it's so powerful and has a lot of expensive hardware upgrades like RAM and lots of drives.
Well, I tried installing the update to Parallels 10 when it came out, and not only did the installer NOT check to see if the new version would run on the hardware before installing, there was absolutely no way to roll back the installation, run Parallels 9 because it was deleted via the installer, AND Parallels doesn't make previous versions available for download. Customer support apologized for the inconvenience and that was the end of their support. Now I have a $6,000 brick that otherwise would have given me many more years of excellent service.
Lots of software companies keep previous versions available for customers who need them, and I have never seen any whose installer programs don't check first to see if what they are about to install will work on the system BEFORE installing AND deleting the previous version.
In my opinion, this is an intentional business practice of Parallels' and is horribly inconsiderate. Especially since this software is doing updates autonomously and intentionally keeping people from choosing to turn off the automatic nature of updates.
It appears that they really embrace the benefits of having a software model that is purely subscription based while marketing it as a product that once you buy it it will just keep working indefinitely as-is if you would prefer that.
I don't see anything in their marketing where they say "This software you paid for will eventually stop working when a new version comes out, either because you chose to upgrade without making sure it will install on your older hardware, OR because we decided to just make the updating process fully automatic."