Stop Killing Games

As others have noted, the problem is often with keeping servers running. It's impossible to predict how successful a game will be in the long term, so the publisher can't make any claims to it's longevity. And, it doesn't make any sense to keep servers running if there's not enough income flow. Where this is really an issue is MMOs. Games like Forza already have some solutions: online features are eventually disabled, but you can still play the core game.

MMOs don't often have a profitability problem, they even tend to overstay their welcome compared to any other game. While it would be nice to get a server binary to self host after they're EoL it's gonna be unfeasible to run it anyway.

The issue is really more with lazy implementations where a server check is required to play something that's fully single player as you say, which has become standard for major publishers now and is far too common for indie games too. It's not too much to ask to do the bare minimum and keep that single instance auth server online or just remove the requirement entirely by commenting out a few lines.