

In large scale computing, a server will have VERY powerful hardware. You can run multiple VMs on that one machine, giving a slice of that power to each VM so that it basically ends up with multiple individual computers running on one very powerful set of hardware instead of building a ton of individual.
Steam very specifically states that you buy a license for the game. Unless someone somehow takes over the license agreements with publishers, your game library disappears.
GOG very plainly states your ability to download game installers to have as a backup to prevent this ever being an issue. They could go under and say “you have 3 days to download your games before servers go offline” and you could.