A dependency required for the software to function no longer exists (like when a game's servers get shutdown) is essentially the same as an object breaking naturally over time due to wear and tear.
There's where your mental model is just wrong. The game server is in the domain of the seller. Some hardware breaking due to wear & tear or abuse is NOT. That is an incredibly important legal distinction.
f you spent $50 when the game launched and played for 500 hours, should you get a refund when the game shuts down 4 years later?
What EXACTLY do you mean with "the game shuts down"? That is the whole point. The game SERVERS shutting down is not the same as disabling the game. If it's an online-only game, there could still be OTHER servers, not run by the seller. Official or unofficial. That is the whole point of "stop killing games".
If your license was revoked because you were cheating, breaking rules, and generally being a complete cunt in some online game
Again, this is relevant for online games only, and is not about the game at all, but about access to a specific community or server. Even if I am the biggest asshole on the planet and every ban was absolutely justified - why should I not be able to set up my own server, invite my equally assholish friends and play there? There is no reason to disable the GAME, only the access to a specific server. These can be two distinct things. You buy the game, but you subscribe to a server.
Come to think of it, how the fuck are they supposed to issue refunds accurately anyway?
They shouldn't create the need to refund. You're making up a problem here. Every refund ever was done at the point of sale for the price you paid. That's why invoices and receipts exist.
You can't steal a contract, which is all the license really is. Your payment gets you a contract.
But that's not what it says. Every shop ever treated games as a SALE. Steam doesn't label the button "buy" anymore, but most other shops still do, and even on Steam everything else is handled exactly like a sale of a product. Shopping cart and all.
Because they want to eat their cake and have it, too. I'm sure players would be more hesitant to part with 60 bucks if it clearly said: "temporary, revocable at any time for any reason, permission to play".