In a lot of juristictions there is a concept called the "natural lifetime" of a product. When you hear a product has a "lifetime warranty" thats what is meant by "lifetime" (its not YOUR lifetime, its the products lifetime). and largely thats a term of art that means roughly "whatever a reasonable person would expect that product would last for". For software this would be "for as long as a computer can still run it". So it would be unreasonable to still expect Powermac software to run in a world where you cant get Powermac's anymore.
And for single player games, a reasonable person would NOT expect that the natural lifetime would be "for however long the company could be bothered to run the DRM server for". A multiplayer game would probably have a different expectation, but the stop killing game campaign is mostly about single player games.
And in a *lot* of juristictions, Europe, Australia and *probably* many US states, all purchases have that "lifetime" warranty by law so there is definitely grounds to say that if a company intentionlly disables a product that otherwise would still run, then the customer is entitled to a full refund, even if its 10 years later.