Turns out that the smart contract is a post-it note stapled to the NFT and the marketplace can just ignore what the post-it note says because it's not legally binding.
What they can't do is trade with marketplaces that do enforce the contract. Originally it was enforced because if one marketplace stopped enforcing it the marketplace would be cut off from the Echo system but turns out that the 5 big marketplaces just need to agree to drop it and everything is fine.
No see it's a lot more sophisticated than that. The post-it note is immutable because of maths or something, so what that means is that it's capital-P Property. And because Property is a magic spell that binds even the old ones, and this spell is unbreakable, I own all these apes.
Basically the transfer function on an erc721 interface (nft) cannot have enforced royalty payment otherwise it wouldn't support people transferring the token outside of a sale. Theoretically you could use some kind of interface standard or write up a different contract where users are forced to pay a royalty on any kind of transfer but then there wouldn't be a way to transfer it without paying the royalty and basically no nft trading platforms would support it because under the hood you have to transfer them the token so they can sell it on your behalf once a buyer is found.
FYI not trying to shill funny pictures but I do know a bit of solidity so maybe someone here is actually curious about the limitation.