I’m really surprised that more automatic update systems don’t make a complete copy of the old image (and keep it in an obvious place) before trying to merge or

I’m really surprised that more automatic update systems don’t make a complete copy of the old image (and keep it in an obvious place) before trying to merge or overwrite changes. Disks are huge, and it would mean that users can simply run the previous version in the event of an unexpected breaking change after an update. The only one I can think of that makes a copy is the one from Omni Group, which seems to leave an old version in the Trash. Plus, it renames the application so it has an exact “version” for clarity.