I still have backed up copies of the full source code of personal projects that I wrote 25 years ago. These will probably never be deleted until I'm dead.
1: One company I worked for didn't have a clue about managing their source code, and didn't even use source control. They were a hardware manufacturer that just didn't understand or care about software at all. Not what I'd think of when I think a professional game developer.
That was fairly typical at the time. It wasn't uncommon for a game publisher to patch their games, it was uncommon for that patching happen too far from the initial release. After all, they wanted their game devs working on something other than the old release. The patches were strictly just a goodwill thing to make sure the game kept selling.
Prior to ~2010 we were simply deleting source code and assets for finished projects; either because they weren't owned by the developer due to a publishing deal, or because the developers didn't want to reuse their garbage code. Same follows for assets, often they were owned by the publisher and not the developer, but if the developer did happen to own them they'd rarely see reuse in future projects. And publishers didn't catch on to the value of data retention until remakes started to make serious money.