Official re-releases of old projects require agreement with copyright holders, adaptation for modern platforms, and commercial viability.
Nobody does it out of good intentions, because that's not how salaries are paid.
According to Gołębiewski, bringing back multiplayer games is a "very complex task," but this topic is actively discussed among players, regulators, and publishers. The Stop Killing Games initiative wants to obligate publishers through EU legislation to create plans for ending support for online games while preserving access to them after server shutdowns. Some companies have already started implementing such solutions: Suicide Squad: Kill the Justice League received an offline mode, and Knockout City allowed players to launch private servers.
GOG strives to "make games timeless," but the director fears that new rules may limit the types of projects that will be funded.
Then publishers will say: "Now we need to allocate funds, promote, and support the game for 10–20 years because the regulator said so. This may lead to fewer interesting games for players.
Stop Killing Games does not require ten years of support: an offline mode or the possibility of private servers is enough so that players can use the games they have purchased.
I don't have a perfect answer yet, but it's good that the discussion is ongoing.