I wouldn’t be surprised if they can even let it expire by simple deciding to no longer support it.

That's one thing, and that's an acceptable risk everyone takes when buying from an online storefront, IMO. Eventually, they're going to stop supporting that, and we all kind of accept and agree to that. But this is them cutting off your access because you haven't played recently. They're not dropping support for the games in question, so this feels a bit unwarranted. What does it actually cost them to store your game license and save file? Is that cost really offset by the price of the games, themselves?

And what do you think will happen if their license servers ever go offline?

If Google Stadia is to be considered precedent, they refunded every purchased game and DLC when they shut down their service earlier this year. I should hope that a similar offering is made from other storefronts should they ever decide to cease operations.