I've also worked on MMOs and the architectures there can get quite hairy, particularly when they're deeply plumbed into shared services and infrastructure that they couldn't operate without. Those layers occasionally have closed-source licensed tech mixed in there.

Untangling the entire lot to make the game available upon closure would be a nightmare in some cases.

I've also contributed to game server emulation (pre-professionally) to keep them alive, so preserving games is a cause I support, even if I don't think it's necessarily always going to be trivial.