Gods Unchanied and CryptoKitties decided to mutually acknowledge each other's NFTs so that they can each sell more NFTs, since they are both NFT sellers first a

Gods Unchanied and CryptoKitties decided to mutually acknowledge each other's NFTs so that they can each sell more NFTs, since they are both NFT sellers first and game developers second. There's no incentives for any game publisher to unilaterally accept NFTs created by other game publishers. And this collaboration only works on a 1:1 basis - there's no good way to generically support all NFTs that come from a collective marketplace in a useful way and no incentives to do so without having your own NFTs acknowledged by others.