Everyone has a smartphone in their pocket these days, if you're at the shop and you see a game you like: See if it's compatible with your PC or if multiplayer servers are still up rather than taking a selfie for once.
No one has to lose money either cause the store can still sell it for slightly above the price they bought it for, but then at least the customer is aware of, and responsible for what they're buying. It's not like the stores can help it, but they are the ones that will have to deal with the angry customers.
Also, I get that the EU has better things to think about, but a law in this case wouldn't be a bad idea: "If you, as a developer or publisher sell a game with a multiplayer mode, you must support this for at least 5 years". Doesn't have to be active support but at least don't shut it down. Then after 5 years it can go in the Expired Games bin.