The idea would be that an NFT would provide a platform-agnostic proof-of-ownership to show that you have the right to download the game from a download provider and to satisfy its DRM protection. Basically a replacement for a license key. License keys are not transferable once redeemed, NFTs are. Modern software ownership models allow the software company to write whatever copyright law they choose, controlling length of ownership, terms of use, transferrability, backups, etc.