I think No Man's Sky is also in the same boat.
I mean games which keep releasing further content over long periods without charging extra for it. Surely the amount of new sales eventually dwindles considerably. Is the cost of new content once you have the core game this low or...?
The vast majority of these "timeless" games seem to come from smaller devs. Minecraft started out indie before being bought out, Terraria is still indie, NMS is a small team etc. They work on those games because they want to, and it makes them enough money to stay satisfied. Games from publicly traded companies are held at gunpoint by their shareholders, so if they don't keep the money machine printing and they don't make it print faster and faster, they will face consequences.
I love how you put it. I think the particular consequences of not making money quickly enough is pulling the plug in projects. Investors want money, not games.