NVIDIA is changing the way games are bundled with its GeForce graphics cards in order to prevent their resale.
Until now when you bought a high-end NVIDIA graphics card, you got a free game voucher that can be redeemed through NVIDIA's website for a key from Steam, Microsoft or Origin. Naturally, many gamers just resold those keys on eBay - essentially giving themselves a small rebate on the cards.
With the new system - now in place - you have to redeem the vouchers through your GeForce Experience account when then links to the relevant store. Following the new changes, NVIDIA updated its code redemption FAQ to stress that the vouchers "are intended for use by the purchaser" alone. The FAQ also states that GeForce Experience will run a hardware check "to ensure that the coupon code is redeemed on the system with the qualifying GPU," the FAQ states. It is unclear though this hardware check will tie the game to one specific card. You might be able to give the code to another user who have an NVIDIA card of the same model; though that would be meaningless since he probably would have the same game already.
A few months ago Microsoft announced a number of people tried to game the system by purchasing a GeForce GTX 1070, using its bundled Gears Of War 4 game voucher then returning the card. It is quite possible that the new policy change was meant to prevent similar situations. Of course it is also possible to be simply a way to get more people to install GeForce Experience.