This happens with iOS apps as well.
But at least on a Mac, it's easier to retain the current version, and downgrading to the last "safe" version is at least possible if one has stashed the installer somewhere.
On iOS, unwittingly upgrade (or worse, find that iOS automatically did it for you) to a newer version that has stripped previously paid-for features, changed business models, revoked "lifetime" status, or other shenanigans under new ownership, and there is no recourse except to delete the app.
(Yes, I'm looking at you, Camera+. And before it, Mercury browser.)
It's one of the worst aspects of the iDevice ecosystem lockdown.