Good analogy. The battle shouldn’t be about forcing abandonware to be opensource. We should focus on DRM, it makes games almost impossible to play when servers shut down.
OP should have compared it to other medias such as movies. When you buy a box copy, you expect it to work long after the authors/studios/etc. are gone.
The issue is about the lack of legal ways to play older games as time moves on. It will only grow bigger in the next few years with even more games relying on DRM and online servers.